C PROGRAM • VARIABLES & ASSIGNMENT

Swap Two Numbers Using a Temporary Variable

Preserve the first value in temporary storage before exchanging two integers.

BeginnerAssignmentTemporary variableInput

PROBLEM UNDERSTANDING

Input and expected output

Sample input

10 25

Sample output

Enter two integers: 10 25
After swapping: 25 10

C PROGRAM

Complete program

#include <stdio.h>

int main(void)
{
    int first, second, temp;
    printf("Enter two integers: " );
    scanf("%d %d", &first, &second);
    temp = first;
    first = second;
    second = temp;
    printf("After swapping: %d %d\n", first, second);
    return 0;
}

First integerSecond integer

CURRENT STEP

Select Start to trace this program.

VARIABLES

Scope	Name	Value
Not started

CALL STACK

main()

PROGRAM OUTPUT

Waiting to run…

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read first and second.
Copy first into temp.
Copy second into first.
Copy temp into second.
Print the exchanged values.

The temporary variable protects the original first value. Without temp, assigning second to first would destroy the value needed for the final assignment.

EFFICIENCY

Time and space complexity

Time complexity

O(1)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Assigning first = second before saving first.

Check this

Printing the original variables before performing all three assignments.