# 随机数

1）stdlib-rand()，每次都是一样的随机数

```c
#include<stdio.h>
#include<stdlib.h>

int main()
{
       for(int i=0;i<10;i++){
             printf("%d \n",rand());
    }
  return 0;
}

/*
(base) jiang@jiangxinfadeAir c % ./random_1
16807 
282475249 
1622650073 
984943658 
1144108930 
470211272 
101027544 
1457850878 
1458777923 
2007237709 
**/
```

2）一定范围内的随机数

加上`rand()%n`

3）不固定带种子的随机数

通常可以利用time(0)的返回值来当做seed

```c
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define random(x) (rand()%x)

int main()
{

     srand((int)time(0));
     for(int x=0;x<10;x++)
           printf("%d \n",random(100));
  return 0;
}


/*
(base) jiang@jiangxinfadeAir c % ./random_2
86 
9 
65 
96 
13 
98 
9 
22 
63 
22 
*/
```


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