Given two numbers, write a C program to swap the given numbers.
Input : x = 10, y = 20; Output : x = 20, y = 10 Input : x = 200, y = 100 Output : x = 100, y = 200
The idea is simple
- Assign x to a temp variable : temp = x
- Assign y to x : x = y
- Assign temp to y : y = temp
Let us understand with an example.
x = 100, y = 200
After line 1: temp = x
temp = 100After line 2: x = y
x = 200After line 3 : y = temp
y = 100
// C program to swap two variables #include <stdio.h> int main() { int x, y; printf("Enter Value of x "); scanf("%d", &x); printf("\nEnter Value of y "); scanf("%d", &y); int temp = x; x = y; y = temp; printf("\nAfter Swapping: x = %d, y = %d", x, y); return 0; } |
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Output:
Enter Value of x 12 Enter Value of y 14 After Swapping: x = 14, y = 12
How to write a function to swap?
Since we want the local variables of main to modified by swap function, we must them using pointers in C.
// C program to swap two variables using a // user defined swap() #include <stdio.h> // This function swaps values pointed by xp and yp void swap(int *xp, int *yp) { int temp = *xp; *xp = *yp; *yp = temp; } int main() { int x, y; printf("Enter Value of x "); scanf("%d", &x); printf("\nEnter Value of y "); scanf("%d", &y); swap(&x, &y); printf("\nAfter Swapping: x = %d, y = %d", x, y); return 0; } |
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Output:
Enter Value of x 12 Enter Value of y 14 After Swapping: x = 14, y = 12
How to do in C++?
In C++, we can use references also.
// C++ program to swap two variables using a // user defined swap() #include <stdio.h> // This function swaps values referred by // x and y, void swap(int &x, int &y) { int temp = x; x = y; y = temp; } int main() { int x, y; printf("Enter Value of x "); scanf("%d", &x); printf("\nEnter Value of y "); scanf("%d", &y); swap(x, y); printf("\nAfter Swapping: x = %d, y = %d", x, y); return 0; } |
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Output:
Enter Value of x 12 Enter Value of y 14 After Swapping: x = 14, y = 12
Is there a library function?
We can use C++ library swap function also.
// C++ program to swap two variables using a // user defined swap() #include <bits/stdc++.h> using namespace std; int main() { int x, y; printf("Enter Value of x "); scanf("%d", &x); printf("\nEnter Value of y "); scanf("%d", &y); swap(x, y); printf("\nAfter Swapping: x = %d, y = %d", x, y); return 0; } |
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Output:
Enter Value of x 12 Enter Value of y 14 After Swapping: x = 14, y = 12
How to swap without using a temporary variable?
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