DATA STRUCTURES PROGRAM • ARRAY TECHNIQUES

Find a Pair Sum with Two Pointers

Learn how to find a pair sum with two pointers using a clear C program.

BeginnerTwo pointersSorted arrayPair sum

PROBLEM UNDERSTANDING

Input and expected output

Sample input
No input required
Sample output
Pair = 2, 14

COMPLETE C PROGRAM

Complete C implementation

dsa-two-pointer-pair-sum.c
Open in compiler
#include <stdio.h>

int main(void)
{
    int values[] = {1, 2, 4, 6, 10, 14};
    int target = 16, left = 0, right = 5;
    while (left < right) {
        int sum = values[left] + values[right];
        if (sum == target) {
            printf("Pair = %d, %d\n", values[left], values[right]);
            return 0;
        }
        if (sum < target) left++;
        else right--;
    }
    puts("No pair found.");
    return 0;
}

GUIDED CODE TOUR • NOT LIVE EXECUTION

Study the program line by line

Use the real compiler button above to run and debug with different inputs.

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Pair = 2, 14
0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

  1. Read the required input values.
  2. Move the left pointer for a small sum and the right pointer for a large sum.
  3. Display the computed result.

Move the left pointer for a small sum and the right pointer for a large sum.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.