Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
587 views
in Technique[技术] by (71.8m points)

c++ - Why does rand() return the same value using srand(time(null)) in this for loop?

I have the following code

#include<iostream>
#include "time.h"

using namespace std;

void printRandomNumber()
{
    srand(time(NULL));
    cout << rand() % 3;
}

int main()
{
    for(int i=0; i<=5; i++)
    {
        printRandomNumber();
    }
system("pause");
}

The output is the same number repeated six times, I would like it to print out a mix of numbers.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

Because you're seeding with the same value each time – time only has second-level precision, and I'm quite sure your computer can process those six loop iterations within one second. ;-]

Seed once, at the beginning of the program.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...