计算交错序列前n项和

Question

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Answer 1

#include <stdio.h>
#include <math.h>
int main()
{
    int i,n;
    float res;
    scanf("%d", &n);
    for(i = 1;i <= n;i++){
        res += pow(-1,i-1)*i/(2*i-1);
    }
    printf("%.3f",res);
    return 0;
}