用C语言实现从文本文件中读取数据后进行排序的功能

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

/*=============================
  制作于：Aug 16,2016
  by QQ:1729403632
===============================*/

#define ST 64 //字符串大小

void mergesort(int *,int);
void _mergesort(int *,int,int *);
void merge(int *,int *);
char * s_gets(char *,int);

int main(int argc,char * argv[]){
  FILE * sor,* dest; //sor源文件 dest目标文件
  int * ptr;//临时数组
  int i,n; //n表示元素个数
  char fname[ST]; //临时存储字符串

  printf("请输入元素个数:");
  while( scanf("%d",&n) != 1 || n <= 0 ){
    printf("输入错误,请重新输入！n");
    while(getchar() != 'n')
      continue;
  }
  while(getchar() != 'n')
      continue;

  ptr = (int *)malloc( (size_t)n * sizeof(int) ); //申请动态数组//////
  if(ptr == NULL){
    fprintf(stderr,"FAIL TO ASK FOR MEMORY SPACEn");
    exit(EXIT_FAILURE);
  }

  printf("请输入原文件名:");
  if( s_gets(fname,ST) == NULL ){
    fprintf(stderr,"Fail to get a stringn");
    exit(EXIT_FAILURE);
  }

  sor = fopen(fname,"r"); //打开包含数据的源文件
  if(sor == NULL){
    fprintf(stderr,"Fail to open the source filen");
    exit(EXIT_FAILURE);
  }

  for(i = 0; i < n; i++) //获取数据到动态数组
    if( fscanf(sor,"%d",&ptr[i]) != 1 ){
      fprintf(stderr,"Fail to get the datan");
      exit(EXIT_FAILURE);
    }

  mergesort(ptr,n); //排序

  printf("请输入要保存数据的文件名：");
  if( s_gets(fname,"Fail to get a stringn");
    exit(EXIT_FAILURE);
  }

  dest = fopen(fname,"w"); //打开目标文件
  if(dest == NULL){
    fprintf(stderr,"Fail to open the destination filen");
    exit(EXIT_FAILURE);
  }

  for(i = 0; i < n; i++){ //输出数据到目标文件
    if( fprintf(dest,"%dt",ptr[i]) < 0 ){
      fprintf(stderr,"Fail to save the datan");
      exit(EXIT_FAILURE);
    }
    if( ((i + 1) % 10) == 0){ //如果写满10个就换行
      if( fprintf(dest,"n") < 0 ){
        fprintf(stderr,"Fail to save the datan");
        exit(EXIT_FAILURE);
      }
    }
  }

  if( fclose(sor) != 0 ){ //关闭源文件
    fprintf(stderr,"Fail to close the source filen");
    exit(EXIT_FAILURE);
  }
  if( fclose(dest) != 0 ){ //关闭目标文件
    fprintf(stderr,"Fail to close the destination filen");
    exit(EXIT_FAILURE);
  }
  free(ptr); //释放内存

  printf("成功完成！n请按任意键继续^ ^bb");

  getch();
  return 0;
}

void mergesort(int * ar,int size){
  if(size > 0){
    int * temp;
    temp = (int *)malloc( (size_t)size * sizeof(int) ); /////
    if(temp == NULL){
      fprintf(stderr,"Fail to ask for MEMORY SPACEn");
      exit(EXIT_FAILURE);
    }
    _mergesort(ar,size - 1,temp); //归并排序
    free(temp);
  }
}

void _mergesort(int * ar,int start,int end,int * temp){
  if(start < end){
    int mid = (start + end) / 2;
    _mergesort(ar,start,mid,temp);  //左子数组排序
    _mergesort(ar,mid + 1,end,temp);  //右子数组排序
    merge(ar,temp);  //合并子数组
  }
}

void merge(int * ar,int p,int q,int r,int * temp){
  int i = p,j = q + 1,k = 0;
  while(i <= q && j <= r){
    if(ar[i] < ar[j])
      temp[k++] = ar[i++];
    else
      temp[k++] = ar[j++];
  }
  while(i <= q)  //如果序列[i...q]存在，追加
    temp[k++] = ar[i++];
  while(j <= r)  //如果序列[j...r]存在，追加
    temp[k++] = ar[j++];

  for(k = 0; k <= (r - p); k++)
    ar[p + k] = temp[k];
}

char * s_gets(char * st,int size){
  char * re;
  int i = 0;

  re = fgets(st,size,stdin);
  if(re){
    while(st[i] != 'n' && st[i] != '') //如果没有到输入字符串结束
      i++;  //递增
    if(st[i] == 'n') //如果字符串最后一个字符是'n'
      st[i] = ''; //把它变成''
    else //否则缓冲区内还有一部分超出读取范围的字符没有被读取
      while(getchar() != 'n') //把这些字符读取完（清空缓冲区）
        continue;
  }

  return re;
}