（Problem 6）Sum square difference

The sum of the squares of the first ten natural numbers is,

1 ² + 2 ² + ... + 10 ² = 385

The square of the sum of the first ten natural numbers is,

(1 + 2 + ... + 10) ² = 55 ² = 3025

Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025  385 = 2640.

Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

 1 #include <stdio.h>

 2 #include <string.h>

 3 #include <ctype.h>

 4 #include <math.h>

 5   

 6 #define N 100

 7   

 8 int powplus(int n, int k)

 9 {

10     int s=1;

11     while(k--)

12     {

13        s*=n;

14     }

15   return s;

16 }

17   

18 int sum1(int n)

19 {

20    return  powplus((n+1)*n/2,2);

21 } 

22   

23 int sum2(int n)

24 {

25    return (n*(n+1)*(2*n+1))/6;

26 }

27   

28 void solve()

29 {

30      printf("%d\n",sum1(N));

31      printf("%d\n",sum2(N));

32    printf("%d\n",sum1(N)-sum2(N));

33 }

34   

35 int main()

36 {

37   solve();

38   return 0;

39 }

 

Answer:

25164150