[BAEL-1641] Find all pairs of numbers in an array that add up to a given sum (#3890)
* [BAEL-1641] Find all pairs of numbers in an array that add up to a given sum * Commiting editor's suggested changes * Commiting article Spring Data Reactive Mongo DB microservice in Kotlin * Revert commit for BAEL 1687 - Moving those files to a new branch * Use AssertJ and BDD-style on unit testing
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Jorge
KevinGilmore
parent
5e78d679d8
commit
5b5386636b
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@ -6,6 +6,7 @@ import com.baeldung.algorithms.ga.annealing.SimulatedAnnealing;
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import com.baeldung.algorithms.ga.ant_colony.AntColonyOptimization;
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import com.baeldung.algorithms.ga.binary.SimpleGeneticAlgorithm;
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import com.baeldung.algorithms.slope_one.SlopeOne;
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import com.baeldung.algorithms.pairsaddupnumber.FindPairs;
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public class RunAlgorithm {
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@ -17,6 +18,7 @@ public class RunAlgorithm {
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System.out.println("3 - Simple Genetic Algorithm");
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System.out.println("4 - Ant Colony");
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System.out.println("5 - Dijkstra");
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System.out.println("6 - All pairs in an array that add up to a given sum");
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int decision = in.nextInt();
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switch (decision) {
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case 1:
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@ -37,6 +39,12 @@ public class RunAlgorithm {
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case 5:
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System.out.println("Please run the DijkstraAlgorithmTest.");
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break;
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case 6:
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final FindPairs findPairs = new FindPairs();
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final int[] input = {1, 4, 3, 2, 1, 4, 4, 3, 3};
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final int sum = 6;
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findPairs.execute(input, sum);
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break;
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default:
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System.out.println("Unknown option");
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break;
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@ -0,0 +1,72 @@
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package com.baeldung.algorithms.pairsaddupnumber;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.stream.IntStream;
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/**
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* Find all different pairs of numbers in an array that add up to a given sum - Complexity O(n)
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*/
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public class DifferentPairs {
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/**
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* Show all different pairs using traditional "for" loop
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*
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* @param input - number's array
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* @param sum - given sum
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* @return - number's array with all existing pairs. This list will contain just one pair's element because
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* the other one can be calculated with SUM - element_1 = element_2
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*/
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public static List<Integer> findPairsWithForLoop(int[] input, int sum) {
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final List<Integer> allDifferentPairs = new ArrayList<>();
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// Aux. hash map
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final Map<Integer, Integer> pairs = new HashMap();
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for (int i : input) {
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if (pairs.containsKey(i)) {
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if (pairs.get(i) != null) {
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// Add pair to returned list
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allDifferentPairs.add(i);
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}
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// Mark pair as added to prevent duplicates
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pairs.put(sum - i, null);
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} else if (!pairs.containsValue(i)) {
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// Add pair to aux. hash map
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pairs.put(sum - i, i);
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}
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}
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return allDifferentPairs;
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}
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/**
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* Show all different pairs using Java 8 stream API
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*
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* @param input - number's array
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* @param sum - given sum
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* @return - number's array with all existing pairs. This list will contain just one pair's element because
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* the other one can be calculated with SUM - element_1 = element_2
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*/
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public static List<Integer> findPairsWithStreamApi(int[] input, int sum) {
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final List<Integer> allDifferentPairs = new ArrayList<>();
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// Aux. hash map
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final Map<Integer, Integer> pairs = new HashMap();
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IntStream.range(0, input.length).forEach(i -> {
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if (pairs.containsKey(input[i])) {
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if (pairs.get(input[i]) != null) {
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// Add pair to returned list
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allDifferentPairs.add(input[i]);
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}
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// Mark pair as added to prevent duplicates
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pairs.put(sum - input[i], null);
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} else if (!pairs.containsValue(input[i])) {
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// Add pair to aux. hash map
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pairs.put(sum - input[i], input[i]);
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}
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}
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);
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return allDifferentPairs;
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}
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}
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@ -0,0 +1,51 @@
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package com.baeldung.algorithms.pairsaddupnumber;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.stream.IntStream;
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/**
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* Find all existing pairs of numbers in an array that add up to a given sum - Complexity O(n^2) "Brute force"
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*/
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public class ExistingPairs {
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/**
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* Show all existing pairs using traditional "for" loop
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*
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* @param input - number's array
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* @param sum - given sum
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* @return - number's array with all existing pairs. This list will contain just one pair's element because
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* the other one can be calculated with SUM - element_1 = element_2
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*/
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public static List<Integer> findPairsWithForLoop(int[] input, int sum) {
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final List<Integer> allExistingPairs = new ArrayList<>();
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for (int i = 0; i < input.length; i++) {
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for (int j = 0; j < input.length; j++) {
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if (j != i && (input[i] + input[j]) == sum) {
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allExistingPairs.add(input[i]);
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}
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}
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}
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return allExistingPairs;
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}
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/**
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* Show all existing pairs using Java 8 stream API
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*
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* @param input - number's array
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* @param sum - given sum
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* @return - number's array with all existing pairs. This list will contain just one pair's element because
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* the other one can be calculated with SUM - element_1 = element_2
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*/
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public static List<Integer> findPairsWithStreamApi(int[] input, int sum) {
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final List<Integer> allExistingPairs = new ArrayList<>();
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IntStream.range(0, input.length).forEach(i ->
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IntStream.range(0, input.length)
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.filter(j -> i != j && input[i] + input[j] == sum)
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.forEach(j -> allExistingPairs.add(input[i]))
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);
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return allExistingPairs;
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}
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}
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@ -0,0 +1,74 @@
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package com.baeldung.algorithms.pairsaddupnumber;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.stream.IntStream;
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public class FindPairs {
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public void execute(int[] input, int sum) {
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final StringBuilder inputArray = new StringBuilder();
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inputArray.append("{");
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IntStream.range(0, input.length).forEach(i -> inputArray.append(input[i] + ", "));
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inputArray.append("}");
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System.out.println(" Given number array: " + inputArray.toString());
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System.out.println(" Given sum: " + sum);
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/* Call services */
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getDifferentPairs(input, sum);
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getExistingPairs(input, sum);
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}
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/**
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* Print all existing pairs for the given inputs: input array & sum number
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*/
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private static void getExistingPairs(int[] input, int sum) {
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List<Integer> pairs = new ArrayList<>();
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System.out.println("~ All existing pairs ~");
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/* Traditional FOR loop */
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// Call method
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pairs = ExistingPairs.findPairsWithForLoop(input, sum);
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// Create a pretty printing
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final StringBuilder output1 = new StringBuilder();
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pairs.forEach((pair) -> output1.append("{" + pair + ", " + (sum - pair) + "}, "));
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// Print result
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System.out.println("Traditional \"for\" loop: " + output1.toString().substring(0, output1.length() - 2));
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/* Java 8 stream API */
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// Call the method
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pairs = ExistingPairs.findPairsWithStreamApi(input, sum);
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// Create a pretty printing
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final StringBuilder output2 = new StringBuilder();
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pairs.forEach((pair) -> output2.append("{" + pair + ", " + (sum - pair) + "}, "));
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// Print result
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System.out.println("Java 8 streams API: " + output2.toString().substring(0, output2.length() - 2));
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}
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/**
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* Print all different pairs for the given inputs: input array & sum number
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*/
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private static void getDifferentPairs(int[] input, int sum) {
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List<Integer> pairs = new ArrayList<>();
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System.out.println("~ All different pairs ~");
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/* Traditional FOR loop */
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// Call method
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pairs = DifferentPairs.findPairsWithForLoop(input, sum);
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// Create a pretty printing
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final StringBuilder output3 = new StringBuilder();
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pairs.forEach((pair) -> output3.append("{" + pair + ", " + (sum - pair) + "}, "));
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// Print result
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System.out.println("Traditional \"for\" loop: " + output3.toString().substring(0, output3.length() - 2));
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/* Java 8 stream API */
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// Call method
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pairs = DifferentPairs.findPairsWithStreamApi(input, sum);
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// Create a pretty printing
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final StringBuilder output4 = new StringBuilder();
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pairs.forEach((pair) -> output4.append("{" + pair + ", " + (sum - pair) + "}, "));
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// Print result
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System.out.println("Java 8 streams API: " + output4.toString().substring(0, output4.length() - 2));
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}
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}
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@ -0,0 +1,39 @@
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package com.baeldung.algorithms.pairsaddupnumber;
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import org.junit.Test;
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import java.util.List;
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import static org.assertj.core.api.Assertions.assertThat;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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public class DifferentPairsUnitTest {
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/* All different pairs */
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@Test
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public void whenTraditionalLoop_thenReturnAllDifferentPairs() {
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/* Data */
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final int[] input = {2, 4, 3, 3, 8};
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final int sum = 6;
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/* Call service */
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final List<Integer> pairs = DifferentPairs.findPairsWithForLoop(input, sum);
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/* Check results */
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assertThat(pairs).hasSize(2).contains(4,3).doesNotContain(8);
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}
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@Test
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public void whenStreamApi_thenReturnAllDifferentPairs() {
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/* Data */
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final int[] input = {2, 4, 3, 3, 8};
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final int sum = 6;
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/* Call service */
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final List<Integer> pairs = DifferentPairs.findPairsWithStreamApi(input, sum);
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/* Check results */
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assertNotNull(pairs);
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assertEquals(pairs.size(),2);
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assertEquals(pairs.get(0), new Integer(4));
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assertThat(pairs).hasSize(2).contains(4,3).doesNotContain(8);
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}
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}
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@ -0,0 +1,34 @@
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package com.baeldung.algorithms.pairsaddupnumber;
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import org.junit.Test;
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import java.util.List;
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import static org.assertj.core.api.Assertions.assertThat;
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public class ExistingPairsUnitTest {
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/* All existing pairs */
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@Test
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public void whenTraditionalLoop_thenReturnAllExistingPairs() {
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/* Data */
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final int[] input = {2, 4, 3, 3, 8};
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final int sum = 6;
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/* Call service */
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final List<Integer> pairs = ExistingPairs.findPairsWithForLoop(input, sum);
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/* Check results */
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assertThat(pairs).hasSize(4).contains(2,4,3,3).doesNotContain(8);
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}
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@Test
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public void whenStreamApi_thenReturnAllExistingPairs() {
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/* Data */
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final int[] input = {2, 4, 3, 3, 8};
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final int sum = 6;
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/* Call service */
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final List<Integer> pairs = ExistingPairs.findPairsWithStreamApi(input, sum);
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/* Check results */
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assertThat(pairs).hasSize(4).contains(2,4,3,3).doesNotContain(8);
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}
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}
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