通过若干次 rand() 使得随机数的和超过 RAND_MAX 的随机次数的期望

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

const int MAXN = 1e8;

int main() {
    printf("rand: 0-%d:\n", RAND_MAX);
    
    long long cnt1 = 0;
    for (int i = 0; i < MAXN; i++)
        for (long long j = 0; j < RAND_MAX; j += rand())
            cnt1++;
    
    printf("%f\n", cnt1 * 1.0 / MAXN);
    
    long long cnt2;
    for (int k = 0; k < 10; k++)
    {
        cnt2 = 0;
        srand((unsigned)time(NULL));
        for (int i = 0; i < MAXN; i++)
            for (long long j = 0; j < RAND_MAX; j += rand())
                cnt2++;
        
        printf("%d: %f\n", k, cnt2 * 1.0 / MAXN);
    }
    
    return 0;
}