看清题目!4都忘记乘了...以及函数fabsl#include <stdio.h>#include <math.h>int main(){ long double pi = 0; int j, flag = 1; for(j=1; ;j+=2) { long double num = 1.0/j*flag; if(fabsl(num) < pow(10, -6)) break; pi += num; flag = -flag; } printf("%.6Lf\n", pi*4); return 0;}