如何查找总和等于给定数字的整数数组中的所有对

import java.util.Arrays;
/**
 * Java Program to find pairs on integer array whose sum is equal to k
 *
 * @author WINDOWS 8
 */public class ProblemInArray{
 
    public static void main(String args[]) {
        int[] numbers = { 2, 4, 3, 5, 7, 8, 9 };
        int[] numbersWithDuplicates = { 2, 4, 3, 5, 6, -2, 4, 7, 8, 9 };
        prettyPrint(numbers, 7);
        prettyPrint(numbersWithDuplicates, 7);
    }
 
    /**
     * Prints all pair of integer values from given array whose sum is is equal to given number.
     * complexity of this solution is O(n^2)
     */
    public static void printPairs(int[] array, int sum) {
 
        for (int i = 0; i < array.length; i++) {
            int first = array[i];
            for (int j = i + 1; j < array.length; j++) {
                int second = array[j];
 
                if ((first + second) == sum) {
                    System.out.printf("(%d, %d) %n", first, second);
                }
            }
 
        }
    }
    /**
     * Utility method to print input and output for better explanation.
     */
    public static void prettyPrint(int[] givenArray, int givenSum){
        System.out.println("Given array : " + Arrays.toString(givenArray));
        System.out.println("Given sum : " + givenSum);
        System.out.println("Integer numbers, whose sum is equal to value : " + givenSum);
        printPairs(givenArray, givenSum);
    }
 
}
Output:Given sum : 7Integer numbers, whose sum is equal to value : 7
(2, 5)
(4, 3) Given array : [2, 4, 3, 5, 6, -2, 4, 7, 8, 9]Given sum : 7Integer numbers, whose sum is equal to value : 7
(2, 5)
(4, 3)
(3, 4)
(-2, 9)

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
/**
 * Java Program to find two elements in an array that sum to k.
 *
 * @author WINDOWS 8
 */public class ArraySumUsingSet {
 
    public static void main(String args[]) {
       prettyPrint(getRandomArray(9), 11);
       prettyPrint(getRandomArray(10), 12);
    }
 
    /**
     * Given an array of integers finds two elements in the array whose sum is equal to n.
     * @param numbers
     * @param n
     */
    public static void printPairsUsingSet(int[] numbers, int n){
        if(numbers.length < 2){
            return;
        }        
        Set set = new HashSet(numbers.length);
        
        for(int value : numbers){
            int target = n - value;
            
            // if target number is not in set then add
            if(!set.contains(target)){
                set.add(value);
            }else {
                System.out.printf("(%d, %d) %n", value, target);
            }
        }
    }
    
    /*
     * Utility method to find two elements in an array that sum to k.
     */
    public static void prettyPrint(int[] random, int k){
        System.out.println("Random Integer array : " + Arrays.toString(random));
        System.out.println("Sum : " + k);
        System.out.println("pair of numbers from an array whose sum equals " + k);
        printPairsUsingSet(random, k);
    }
    
    /**
     * Utility method to return random array of Integers in a range of 0 to 15
     */
    public static int[] getRandomArray(int length){
        int[] randoms = new int[length];
        for(int i=0; i<length; i++){
            randoms[i] = (int) (Math.random()*15);
        }
        return randoms;
    }
 
}
Output:Random Integer array : [0, 14, 0, 4, 7, 8, 3, 5, 7]
Sum : 11
pair of numbers from an array whose sum equals 11
(7, 4)
(3, 8)
(7, 4) Random Integer array : [10, 9, 5, 9, 0, 10, 2, 10, 1, 9]
Sum : 12
pair of numbers from an array whose sum equals 12
(2, 10)

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
/**
 * Java Program to find all pairs on integer array whose sum is equal to k
 *
 * @author WINDOWS 7
 */public class PrintArrayPairs {
 
    public static void main(String args[]) {
       prettyPrint( new int[]{ 12, 14, 17, 15, 19, 20, -11}, 9);
       prettyPrint( new int[]{ 2, 4, 7, 5, 9, 10, -1}, 9);
    }
 
    /**
     * Given a number finds two numbers from an array so that the sum is equal to that number k.
     * @param numbers
     * @param k
     */
    public static void printPairsUsingTwoPointers(int[] numbers, int k){
        if(numbers.length < 2){
            return;
        }
        Arrays.sort(numbers);
        
        int left = 0; int right = numbers.length -1;
        while(left < right){
            int sum = numbers[left] + numbers[right];
            if(sum == k){
                System.out.printf("(%d, %d) %n", numbers[left], numbers[right]);
                left = left + 1;
                right = right -1;
                
            }else if(sum < k){
                left = left +1;
                
            }else if (sum > k) {
                right = right -1;
            }
        }
       
    }
    
    /*
     * Utility method to print two elements in an array that sum to k.
     */
    public static void prettyPrint(int[] random, int k){
        System.out.println("input int array : " + Arrays.toString(random));
        System.out.println("All pairs in an array of integers whose sum is equal to a given value " + k);
        printPairsUsingTwoPointers(random, k);
    }
    
}
Output :
input int array : [12, 14, 17, 15, 19, 20, -11]All pairs in an array of integers whose sum is equal to a given value 9
(-11, 20)
input int array : [2, 4, 7, 5, 9, 10, -1]All pairs in an array of integers whose sum is equal to a given value 9
(-1, 10)
(2, 7)
(4, 5)