用c语言，用3种循环分别计算圆周率

1. for循环计算圆周率

#include <stdio.h>

int main() {
    int n = 1000000; // 迭代次数
    double pi = 0.0;
    double sign = 1.0;

    for (int i = 1; i <= n; i++) {
        pi += sign / (2 * i - 1);
        sign = -sign;
    }

    pi *= 4;
    printf("pi = %f\n", pi);
    return 0;
}

2. while循环计算圆周率

#include <stdio.h>

int main() {
    int n = 1000000; // 迭代次数
    double pi = 0.0;
    double sign = 1.0;
    int i = 1;

    while (i <= n) {
        pi += sign / (2 * i - 1);
        sign = -sign;
        i++;
    }

    pi *= 4;
    printf("pi = %f\n", pi);
    return 0;
}

3. do-while循环计算圆周率

#include <stdio.h>

int main() {
    int n = 1000000; // 迭代次数
    double pi = 0.0;
    double sign = 1.0;
    int i = 1;

    do {
        pi += sign / (2 * i - 1);
        sign = -sign;
        i++;
    } while (i <= n);

    pi *= 4;
    printf("pi = %f\n", pi);
    return 0;
}