常用库函数&文件操作函数

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

int cmp(const void *a, const void *b)
{
return *(int*)a - *(int*)b;
}

int main()
{
int a;

//重定向输入流
/*
freopen("input.txt","r",stdin);
*/
//读取和写入文本文件
/*
FILE* fp = fopen("input.txt","r");
FILE* ofp = fopen("output.txt","w");
while(fscanf(fp,"%d",&a) != EOF)
fprintf(ofp,"%d\n",a);
fclose(fp);fclose(ofp);
*/
//读取和写入二进制文件
/*
FILE* fp = fopen("input.txt","rb");
FILE* ofp = fopen("output.txt","wb");
char buf[6];
int cnt;
while(( cnt = fread(buf, sizeof(char), 6, fp)) != 0)
{
for(int i = 0; i < cnt; ++i) putchar(buf[i]);
fwrite(buf, sizeof(char), cnt, ofp);
}
fclose(fp),fclose(ofp);
*/

int as[10] = {0,2,5,8,7,4,1,3,6,9};
qsort(as, 10, sizeof(int), cmp);
for(int i = 0; i < 10; ++i) printf("%d ",as[i]);
return 0;
}