C Exercises: Find the number of combinations that satisfy p + q + r + s = n

C Basic Declarations and Expressions: Exercise-147 with Solution

Write a C program to find the number of combinations that satisfy p + q + r + s = n where n is a given number <= 4000 and p, q, r, s in the range of 0 to 1000.

Sample Solution:

C Code:

#include <stdio.h>
#include <stdlib.h>
#define check_num(x) (x>0?x:0)
int n,result,x;
int main(void){
	printf("Input a positive integer:\n");
	scanf("%d",&n);
		result=0;
		for(x=check_num(n-2000);x<=2000 && n>=x;x++){
			result+=(1001-abs(1000-(n-x)))*(1001-abs(1000-x));
		}
		printf("\nNumber of combinations of p,q,r,s:\n");
		printf("%d\n",result);
	return 0;
}

Sample Output:

Input a positive integer:
25

Number of combinations of p,q,r,s:
3276

Flowchart:

C programming Code Editor:

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