C语言实现文件内容按行随机排列的算法示例

#!/bin/sh
### note: sh random.sh in_fname out_fname ###
infile=$1
outfile=$2
line_num=`cat $infile | wc -l `
./random $line_num $infile $outfile.tmp
sort $outfile.tmp -k 2 -n -t ' ' | cut -f1 > $outfile

//random.c
#include <string>
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
const int LEN = 4098;
//返回属于[p,q)的随机整数
int rand(int p, int q)
{
   int size = q-p+1;
   return p+ rand()%size;
}
//交换两个元素值
void swap(int& a , int& b)
{
   int temp = a;
   a = b;
   b = temp;
}
//打印数组值
void print(int *v, int n)
{
    for(int i=0; i < n ; i++)
    {
        printf("%u\n", v[i]);
    }
}
//给数组a[n], 随机不重复赋值[1,n]之间的数
void randomize(int *v, int n)
{
    //initialize
    for(int i=0; i < n; i++)
    {
        v[i] = i+1;
    }
    for(int i=n-1; i>0; i--)
    {
        int r = rand(0,i+1);
        swap(v[r], v[i]);
    }
}
//删除换行符
int chomp(char *str)
{
  int len = strlen(str);
  while(len > 0 && (str[len - 1] == '\n' || str[len - 1] == '\r'))
  {
    str[len - 1] = 0;
    len--;
  }
  return len;
}
//主函数
int main(int argc, char *argv[])
{
    int line_num = atoi(argv[1]);
    printf("%u\n",line_num);
    int *value = (int*)malloc((line_num) * sizeof(int));
    printf("%u\n",line_num);
    randomize(value, line_num);
    //print(value, N);
    FILE* infile = fopen(argv[2], "r");
    if( infile == NULL )
    {
        printf("Cann't open file %s.", argv[1]);
        return 0;
    }
    FILE* outfile = fopen(argv[3], "w");
    if( outfile == NULL)
    {
        printf("Cann't open file %s to write.", argv[2]);
        return 0;
    }
    int i=0;
    char str[LEN];
    str[0] = 0;
    str[LEN-1] = 0;
    while( !feof(infile) )
    {
        if( !fgets(str, sizeof(str),infile))
        {
            break;
        }
        str[LEN- 1] = 0;
        chomp(str);
        fprintf(outfile, "%s\t%u\n", str, value[i]);
        i++;
    }
    fclose(infile);
    fclose(outfile);
    return 0;
}