基本用法：
1. freopen("2010_1.txt","r",stdin)
freopen("2010_1_e.txt","w",stdout);
2. FILE *pr,*pw;
pr = fopen("2010_1.txt","r");
fgets(tmp,100,pr); // tmp 是char[] 数组，100 是数组长度
pw = fopen("2010_1_e.txt","w");
fputs(tmp,pw);
fclose(pr);
fclose(pw);
3. 在文件操作的过程中，经常需要用到整数和字符数组之间的转换，函数是
int atoi(const char *nptr); // 字符串转换成整数
以及
char*itoa(intvalue,char*string,intradix);// 整数转换成字符串sprintf();字符串格式化命令，主要功能是把格式化的数据写入某个字符串中。sprintf 是个变参函数。eg.格式化读写函数：fscanf和fprinf
#include <iostream>
using namespace std;
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <map>
char str[360];
int key,keys;
int main(){
FILE *fi = fopen("in.txt","r");
FILE *out = fopen("out.txt","w");
int cnt = 0;
while(fscanf(fi,"%d\t%s",&key,str)!= EOF){
cnt ++;
cout << cnt << " " << endl;
fprintf(out,"%d %s\n",key,str);
}
///system("pause");
}
字符读写函数 ：fgetc和fputc
#include <iostream>
using namespace std;
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <map>
char str[360];
int key,keys;
char ch;
int main(){
//FILE *fi = fopen("in.txt","r");
FILE *out = fopen("out.txt","w");
while((ch=getchar()) != EOF){
fputc(ch,out);
}
///system("pause");
}
#include <iostream>
using namespace std;
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <map>
char str[360];
int key,keys;
char ch;
int main(){
//FILE *fi = fopen("in.txt","r");
FILE *out = fopen("out.txt","r");
while((ch = fgetc(out)) != EOF){
putchar(ch);
}
system("pause");
fclose(out);
}
字符串读写函数：fgets和fputs
数据块读写函数：fread和fwrite
#include <stdio.h>
#include <stdlib.h>
int main(){
FILE *fp = fopen("in.txt","r");
if(fp == NULL){
printf("不能打开文件\n");
exit(0);
}
int i;
struct student{
char name[10];
int age;
double score[2];
char addr[15];
};
struct student stu;
for(i = 0;i < 1;i++){
fread(&stu,sizeof(stu),1,fp);
printf("%s %d %lf %lf %s\n",stu.name,stu.age,stu.score[0],stu.score[1],stu.addr);
}
system("pause");
}
#include <stdio.h>
#include <stdlib.h>
int main(){
FILE *fp = fopen("out.txt","w");
if(fp == NULL){
printf("不能打开文件\n");
exit(0);
}
int i;
struct student{
char name[10];
int age;
double score[2];
char addr[15];
};
struct student stu;
printf("输入姓名 年龄 分数1 分数2 地址\n");
for(i = 0;i < 1;i++){
scanf("%s %d %lf %lf %s",stu.name,&stu.age,&stu.score[0],&stu.score[1],stu.addr);
fwrite(&stu,sizeof(stu),1,fp);
}
}
#include <stdio.h>
#include <stdlib.h>
int main(){
char str[20];
double f=14.309948;
sprintf(str,"%6f%6f%d",f,f,1);
printf("%s\n",str);
system("pause");
}
结果：
下面直接上代码：
第一个例子：将一个文件中的边输出出来（但是是不带权值的边）
#include <iostream>
using namespace std;
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
int main(){
char f[100];
int ff = 0;
FILE *pr,*pw;
int a,b,c;
pr = fopen("1990_1.net","r");
pw = fopen("1990_1.txt","w");
while(fgets(f,100,pr)){
if(ff == 2){
fputs(f,pw);
}
else{
if(f[0] == '*'){
ff += 1;
}
}
}
fclose(pr);
fclose(pw);
freopen("1990_1.txt","r",stdin);
freopen("1990_1_e.txt","w",stdout);
while(scanf("%d %d %d",&a,&b,&c) != EOF){
printf("%d %d\n",a,b);
}
//system("pause");
}
另外一个例子： 实现的功能：将一个文件输出到多个文件
#include <iostream>
using namespace std;
#include <fstream>
#include <string>
int main ()
{
string s;
FILE *pw;
FILE *pr;
char tmp[10000];
char fno[20]; //
char st[10000][20];
int f = 1;
int t = 0; //
pr = fopen("t_2010.txt","r");
pw = NULL;
while(fgets(tmp, 10000, pr)) //
{
if(tmp[0] == '*')
{
f ^= 1;
if(f == 0)
{
if(pw != NULL)
fclose(pw);
t++;
itoa(t,fno,10);
strcpy(st[t],"2010_");
strcat(st[t],fno);
strcat(st[t],".net");
pw = fopen(st[t],"w");
}
}
fputs(tmp, pw);
}
fclose(pw);
fclose(pr);
}
freopne 和getline 用法举例
#include <iostream>
using namespace std;
#include <string>
#include <queue>
#define MAXNode 630000
#define MAXEdge 6000000
int head[MAXNode];
struct edge{
int next;
int w;
int v; // ±ßµÄÄ©¶Ë½Úµã
}edge[MAXEdge];
bool hash[MAXNode]; // ¼Ç¼¸Ã¶¥µãÊÇ·ñÒѾ±»Ëѹý
int hash_conn[MAXNode]; // hash_conn[i] ±íʾ ½ÚµãÊýΪiµÄÁ¬Í¨·ÖÖ§¸öÊýΪhash_conn[i]
int edge_num = 0; // ¼Ç¼±ßµÄÊýÄ¿
int part_num ;
void add(int v1, int v2, int weight){
edge[edge_num].next = head[v1];
edge[edge_num].v = v2;
edge[edge_num].w = weight;
head[v1] = edge_num++;
}
void dfs(int m){
part_num ++;
//cout << m << " " ;
hash[m] = true;
for(int j = head[m];j != -1; j = edge[j].next)
{
if(hash[edge[j].v] == false)
{
dfs(edge[j].v);
}
}
}
void bfs(int m){
queue<int>Q;
while(!Q.empty())
{
Q.pop();
}
Q.push(m);
hash[m] = true;
while(!Q.empty())
{
int tq = Q.front();
Q.pop();
//cout << tq << " ";
part_num ++;
for(int j = head[tq]; j != -1; j = edge[j].next)
{
if(hash[edge[j].v] == false)
{
hash[edge[j].v] = true;
Q.push(edge[j].v);
}
}
}
}
int main()
{
freopen("2009.net","r",stdin);
freopen("2009.txt","w",stdout);
int t[10]; // ¼Ç¼ÁÙʱµÄ±ßȨÐÅÏ¢ t[0] ´ú±í½Úµãv1£¬t[1]´ú±í½Úµãv2£¬t[2]´ú±íȨֵw
int N; // ´ú±í×ܵĽڵãÊý
string str;
bool tag = false; // ÅжÏÊÇ·ñ¶Áµ½±ßȨÐÅÏ¢
memset(head, -1, sizeof(head)); // ¶Ôhead¸³Öµ
while(getline(cin,str))
{
if(tag == true)
{
int tmp = 0, num = 0;
for(int i = 0;i < str.length();i++)
{
if(str[i] >= '0' && str[i] <= '9')
{
tmp = tmp * 10 + str[i] - '0';
}
else if(str[i] == ' ')
{
t[num ++] = tmp;
tmp = 0;
}
}
t[num] = tmp;
add(t[0],t[1],t[2]);
add(t[1],t[0],t[2]);
continue;
}
if(str.substr(0,9) == "*Vertices")
{
int tmp = 0;
for(int i = 9;i < str.length();i++)
{
if(str[i] >= '0' && str[i] <= '9')
{
tmp = tmp * 10 + str[i] - '0';
}
}
N = tmp;
//cout << N << endl;
}
else if(str.substr(0,5) == "*Arcs")
{
tag = true;
}
}
memset(hash, false, sizeof(hash));
memset(hash_conn, 0, sizeof(hash_conn));
int maxt = -1;
for(int i = 1;i <= N;i++)
{
if(hash[i] == false)
{
part_num = 0;
//dfs(i);
bfs(i);
//cout << "part_num = " << part_num << endl;
hash_conn[part_num] ++;
if(part_num > maxt)
maxt = part_num;
}
}
//cout << endl << maxt << endl;
for(int i = 1;i <= maxt; i++)
{
//if(hash_conn[i])
printf(",%d,%d",i,hash_conn[i]);
}
}
递归遍历文件夹举例：
#include <io.h>
#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
#include <cstdlib>
#include <fstream>
#include <map>
using namespace std;
#define MAXNODE 550000
char str[3600000];
char tmp[10000];
// 工具函数：拼接两个字符串s1+s2，返回拼接后的字符串
char* addStr(const char* s1, const char* s2)
{
int l1 = strlen(s1), l2 = strlen(s2);
char* ret = new char[l1+l2+1];
strcpy(ret, s1);
strcpy(ret+l1,s2);
ret[l1+l2] = 0;
return ret;
}
// 工具函数：拼接三个字符串s1+s2+s3，返回拼接后的字符串
char* addStr(char* s1, char* s2, char* s3)
{
return addStr(addStr(s1,s2),s3);
}
// 工具函数：检测是否为正常目录名，即并非仅由'.'组成
inline bool normal_dir_name(char* name)
{
char* p = name;
while(*p == '.')
p++;
return *p;
}
/**********************************************************************
功能： 递归遍历给定目录中所有子目录与文件
参数： path为将进行遍历的目标目录，必须以\\结尾的字符串，例如".\\"
注释： _finddata_t 结构体中包含以下重要的字段：
long attrib; // 文件属性，_A_HIDDEN（隐藏）、_A_NORMAL（正常）
// _A_RDONLY（只读）、_A_SUBDIR（文件夹）、_A_SYSTEM（系统）
time_t time_create; // 文件创建时间
time_t time_access; // 文件最近被访问时间
time_t time_write; // 文件最近被修改时间
_fsize_t size; // 文件大小，字节为单位
char name[_MAX_FNAME]; // 文件名
**********************************************************************/
void dirList(char* path)
{
printf("-------------------%s------------------------\n",path);
struct _finddata_t info;
//printf("%s\n",(addStr(path,"*")));
long handle = _findfirst(addStr(path,"*"), &info); // *为通配符，如*.exe亦可
if(handle == -1)
{
printf("Fail to read the dir!\n");
_findclose(handle);
return;
}
bool over = false;
while(!over)
{
if(normal_dir_name(info.name)) // .与..不纳入处理范围
{
if((info.attrib&_A_SUBDIR) && (info.attrib&_A_HIDDEN)==0){ //子目录递归处理 == 比 && y优先级高
dirList(addStr(path,info.name,"\\"));// 做了转义处理
}
else{ // 普通文件处理，Here to add your code....
tmp[0] = 0;
strcpy(tmp,path);
printf("%s ",info.name);
strcat(tmp,info.name);
// FILE *pr_pre = freopen(tmp,"r",stdin);
FILE *pr_pre = fopen(tmp,"r");
/*if(pr_pre == NULL)
printf("error\n");
else{
printf("open() succ\n");
}*/
map <int,bool> maps;
while(fgets(str,3600000,pr_pre)){
int i;
int key = 0;
for(i = 0;;i++){
if(str[i] != ':'){
key = key * 10 + str[i] - '0';
}
else
break;
}
while(str[i++] != 0){
int tp = 0;
for(;str[i] != ' ' && str[i] != 0;i++){
tp = tp * 10 + str[i] - '0';
}
maps[tp] = true;
if(str[i+1] == '\n')
break;
}
}
int cnt = 0;
for(int i = 0;i < MAXNODE;i++){
if(maps[i] == true)
cnt++;
}
printf("%d\n",cnt);
}
}
over = _findnext(handle, &info);
}
_findclose(handle);
return;
}
int main() // test
{
freopen("out.txt","w",stdout);
dirList("F:\\2014-06-20\\社团演化谱系图\\CPM结果\\"); // for \\ 也是做了转义处理
getchar();
return 0;
}
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