产生0~N-1之间随机数

#include<stdio.h>
#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <stdint.h>
//return 0~N-1
int rand_n(int n){
    uint64_t x=(RAND_MAX+1)/n;
    uint64_t cap=x*n;
    uint64_t r=0;
    do{
        r=rand();
    }while(r>=cap);
    return r/x;
}

int main(){
    srand((int)time(0));
    for(int i=0;i<10;i++){
        std::cout<<rand_n(3)<<std::endl;
    }
    return 0;
}

Reference:
[1] how-to-generate-uniform-distribution
[2] How do I get a specific range of numbers from rand