Print all pairs of values a sorted array that sum up to a given value M

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Question

Print all pairs of values a sorted array that sum up to a given value M

Example

 

Solution

1. Scan from both ends, calculate the sum

2. if(sum is equal to M), print and shrink the focus window

3. if(sum is less than M), shift left focus index by 1

4. if(sum is bigger than M), shift right focus index by 1

5. Stop the loop when left is larger or equal to right index

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package org.fool.java.test;

public class PrintAllPairsSumToM {
    public static void main(String[] args) {
        int[] sorted = {1, 2, 3, 4, 8, 9, 9, 10};
        printAllPairs(sorted, 12);
    }

    private static void printAllPairs(int[] sorted, int m) {
        int left = 0;
        int right = sorted.length - 1;

        while (left < right) {
            int tempSum = sorted[left] + sorted[right];

            if (tempSum == m) {  // which means we find one pair
                System.out.println("Sum of {" + sorted[left] + ", " + sorted[right] + "} = " + m);

                // update the both index values
                left++;
                right--;
            } else if (tempSum > m) { // which means the temp sum is bigger than m
                right--;    // shift right focus index by 1
            } else {    // which means the temp sum is smaller than m
                left++; // shift left focus index by 1
            }
        }
    }
}

Console Output

 

Reference

https://www.youtube.com/watch?v=l5orcTJlT54&list=PLlhDxqlV_-vkak9feCSrnjlrnzzzcopSG&index=39