求1-1/2+1/3-1/4+1/5-1/6+…1/n用while循环
include<stdio.h>int main(){ int a,b,n; double m,i,sum; a = 0;b = 1; m = 1.0;i = 1.0;sum = 0.0; scanf("%d",&n); while(a < n) { sum += m; a++; b = -b; i++;
