字符串反转
#include "stdafx.h"
#include<iostream>
using namespace std;
char*reverse_str(char*str);
int _tmain(int argc, _TCHAR* argv[])
{
char*str = "abcdefgh";
char*dst = reverse_str(str);
cout << dst << endl;
system("pause");
return 0;
}
char*reverse_str(char*str)
{
char*dst=new char[strlen(str)+1];
*dst = ' ';
while (*str != ' ')
{
*(--dst) = *(str++);
cout << *dst << endl;
}
return dst;
}atoi
// my_atoi.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include<iostream>
using namespace std;
int my_atoi(char*in);
int _tmain(int argc, _TCHAR* argv[])
{
char*in = "0123h4dfdd";
cout << atoi(in) <<endl;
cout << my_atoi(in) << endl;
system("pause");
return 0;
}
int my_atoi(char*in)
{
int kk = 0;
int sum = 0;
while (*in <= '9'&&*in >= '0')
{
int kk=*in-'0';
sum = sum*10+kk;
++in;
}
return sum;
}
itoa
// my_itoa.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include<iostream>
using namespace std;
char*my_itoa(int value, char *string, int radix)
{
int k = 0;
int m;
int a = value;
while (a > 0)
{
k++;
a = a / radix;
}
string[k] = ' ';
while (k > 0)
{
m = value%radix;
string[k - 1] = m + '0';
value = value / radix;
--k;
}
return string;
}
int _tmain(int argc, _TCHAR* argv[])
{
char*str=new char[10000];
cout << my_itoa(132, str, 2) << endl;
system("pause");
return 0;
}
编写一个程序实现功能：将两个字符串合并为一个字符串并且输出，用指针实现。
</pre><pre name="code" class="cpp">#include "stdafx.h"
#include<iostream>
using namespace std;
char*my_strcat(char*src, char*dst)
{
char*p = dst;
while (*p != ' ')
p++;
while (*src != ' ')
{
*p = *src;
p++;
src++;
}
*p = ' ';
return dst;
}
int _tmain(int argc, _TCHAR* argv[])
{
char*src = new char[100];
strcpy(src, "RST");
char*dst = new char[100];
strcpy(dst, "ggggg");
cout << my_strcat(src, dst);
system("pause");
return 0;
}
子字符串的替换（C语言）
描述：编写一个字符串替换函数，如函数名为 StrReplace(char* strSrc, char* strFind, char* strReplace)，strSrc为原字符串，strFind是待替换的字符串，strReplace为替换字符串。
举个直观的例子吧，如：“ABCDEFGHIJKLMNOPQRSTUVWXYZ”这个字符串，把其中的“RST”替换为“gggg”这个字符串，结果就变成了： ABCDEFGHIJKLMNOPQggggUVWXYZ
// StrReplace.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include<iostream>
using namespace std;
char*StrReplace(char* strSrc, char* strFind, char* strReplace)
{
char*p1 = strSrc;
char*p2 = strFind;
char*p=NULL;
bool flag = false;
while (*p1 != ' ')
{
if (*p1 == *p2)
{
p = p1;
while (*p1 == *p2&&*p1 != ' ')
{
p1++;
p2++;
if (*p2 == ' ')
{
flag = true;
break;
}
}
}
else
p1++;
if (flag)
break;
}
if (flag)
{
char*p3=new char[100];
//char*p4 = p3;
char*p5 = p1;
//while (*p1 != ' ')
// *(p3++) = *(p1++);
strcpy(p3, p1);
//*p3 = ' ';
while (*strReplace != ' ')
{
*p = *strReplace;
p++;
strReplace++;
}
while (*p3 != ' ')
{
*(p) = *(p3);
++p;
++p3;
}
*p = ' ';
}
return strSrc;
}
int _tmain(int argc, _TCHAR* argv[])
{
char*src = new char[100];
strcpy(src, "ABCDEFGHIJKLMNOPQRSTpVWXYZ");
//src = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";不能直接传const char*类型的值，否则在程序中无法改变值
char*find = new char[100];
//char*find = "RST";
strcpy(find, "RST");
char*replace = new char[100];
strcpy(replace, "ggggg");
//char*replace = "ggggggggg";
cout << StrReplace(src, find, replace) << endl;
system("pause");
return 0;
}
字符串分割
int split(const std::string& str, std::vector<std::string>& ret_, std::string sep = ",")
{
if (str.empty())
{
return 0;
}
std::string tmp;
std::string::size_type pos_begin = str.find_first_not_of(sep);
std::string::size_type comma_pos = 0;
while (pos_begin != std::string::npos)
{
comma_pos = str.find(sep, pos_begin);
if (comma_pos != std::string::npos)
{
tmp = str.substr(pos_begin, comma_pos - pos_begin);
pos_begin = comma_pos + sep.length();
}
else
{
tmp = str.substr(pos_begin);
pos_begin = comma_pos;
}
if (!tmp.empty())
{
ret_.push_back(tmp);
tmp.clear();
}
}
return 0;
}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
#include<stdio.h>/*某个stdio.h*/
int main()/*主函数“整数”类型*/
{
char buffer[50];/*“字符”类型的数组，下面共有50个元素。*/
int n,a=5,b=3;/*三个变量都为“整数”类型,int中间要有空格*/
n=sprintf(buffer,"%d plus %d is %d",a,b,a+b);/*赋予数值*/
printf("[%s]is a string %d chars long
",buffer,n);/*“格式输出函数”*/
return 0;/*“返回零”
也就是程序正常退出*/
}
输出结果：
5 plus 3 is 8
下面这个函数处理文本很有用
fscanf
#include <stdio.h>
FILE *stream;
int main(void)
{
long l;
float fp;
char s[81];
char c;
stream = fopen("fscanf.out", "w+");
if(stream==NULL)
printf("The file fscanf.out was not opened
");
else
{
fprintf(stream,"%s%ld%f%c","a-string", 65000,3.14159, 'x');
/*将指针设置至文件开头*/
fseek(stream,0L,SEEK_SET);
/*从文件中读取数据*/
fscanf(stream,"%s",s);
fscanf(stream,"%ld",&l);
fscanf(stream,"%f",&fp);
fscanf(stream,"%c",&c);
/*输出读取的数据*/
printf("%s
",s);
printf("%ld
",l);
printf("%f
",fp);
printf("%c
",c);
fclose(stream);
}
return 0;
}
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