随机数的产生

#include "stdafx.h"
#include <iostream> 
#include <time.h> 
#include <assert.h> 
using namespace std;
int main()
{
    const int size = 10000000;
    int n;
    int* num = new int[10000000];
    //int num[size];
    FILE *fp = fopen("data.txt", "w");
    assert(fp);

    for (n = 1; n <= size; n++)
        //之前此处写成了n=0;n<size。导致下面有一段小程序的测试数据出现了0，特此订正。 
        num[n] = n;
    srand((unsigned)time(NULL));
    int i, j;

    for (n = 0; n < size; n++)
    {
        i = (rand() * RAND_MAX + rand()) % 10000000;
        j = (rand() * RAND_MAX + rand()) % 10000000;
        swap(num[i], num[j]);
    }

    for (n = 0; n < size; n++)
        fprintf(fp, "%d ", num[n]);
    fclose(fp);
    return 0;
}