# Find all pairs of number whose sum is equal to a given number in C++

This C++ program is able to find all the pairs of numbers in an array whose sum is equal to a specific number by using a nested loop and conditional statements. This problem is based on the application of array which is useful in many places. Following is a short and simple solution to the above task.

## How to find all the pairs of number in an array whose sum is equal to a given number

**Problem statement**

There is an array of size n where n is the number of elements in it. Find all the pair of numbers whose sum is equal to a number given by the user.

- The size of array is given by user.
- Array elements cal be in any order.

**Problem approach**

- Declare an array of size n.
- Store the array elements as per the user input.
- Take the input
- Find the required pairs of numbers and print them on the screen.

#### Program/Source code

Following C++ program is able to find all the pair of numbers in an array whose sum is equal to a given number, is written and successfully compiled in CodeBlocks v16.01 .

/* C++ program to find the pairs of number present in array whose sum is equal to a given number** ***give different sizes for array & the their values to get different result*** ** enter a valid number sum otherwise noting will print on screen ** */ #include <iostream> using namespace std; int main() { int size, num; cout<<"Enter the size of array: "; cin>>size; int array[size]; // array declaration cout<<"Enter array elements: "; for(int i=0;i<size;i++) cin>>array[i]; // input array values cout<<"Enter the number whose pairs are to be found: "; cin>>num; for(int i=0;i<size-1;i++){ // nested for loop for(int j=i+1;j<size;j++){ if(array[i]+array[j]==num) cout<<array[i]<<" and "<<array[j]<<endl; // print pairs } } return 0; }

**Output Example**

Enter the size of array: 8 Enter array elements: 5 6 4 1 5 3 9 8 Enter the number whose pairs are to be found: 9 5 and 4 6 and 3 4 and 5 1 and 8 Process returned 0 (0x0) execution time : 26.536 s Press any key to continue.

**Program explanation**

- Initialize an array and store values in it.
- Take the number input from the user whose pairs are needed to find out.
- Use nested loop statements and conditional statements to find the pairs.
- Print the pairs on the screen.

Also read

Find nature of roots and actual roots of Quadratic equation in C++

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