字符串和int转换函数实现

//不使用库函数将整数转换为字符串，输入 int 输出 char*

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

char* IntoString(int num);     //转换函数
int main(int argc, char** argv)
{
    char *p1 = IntoString(-123);
    char *p2 = IntoString(13345666);
    while(*p1!=‘\0‘)
    std::cout<<*(p1++);
    std::cout<<std::endl;
    while(*p2!=‘\0‘)
    std::cout<<*(p2++);
    std::cout<<std::endl;
    delete p1;
    delete p2;
    return 0;
}
char* IntoString(int num)
{
    int length = 0;
    if(num == 0)
    {
        return NULL ;
    }
    int temp_num = (num > 0 ? num: -num);
    while(temp_num!=0)                     //求正数的长度
    {
        ++length;
        temp_num/=10;
    }
    int Yu = 0;
    if(num>0)                              //处理正整数
    {
        char *pstr = new char[length + 1];
        pstr[length] = ‘\0‘;
        int Op_num = num;
        int n = length-1;
        while(Op_num !=0)
        {
            Yu = Op_num % 10;
            pstr[n--] =  Yu+‘0‘;
            Op_num /= 10;    
        }
        return pstr;
    }
    else
    {
        char *pstr = new char[length + 2];    //处理负整数
        pstr[length+1] = ‘\0‘;
        int Op_num = -num;
        int n = length;
        while(Op_num !=0)
        {
            Yu = Op_num % 10;
            pstr[n--] =  Yu+‘0‘;
            Op_num /= 10;    
        }
        pstr[0] = ‘-‘;
        return pstr;    
    }        
}

//不使用库函数将字符串转换为整数
//karllen   

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int StringToInt(const char *pstr);
int main(int argc, char** argv)
{
    char one[] = "1234";
    char two[] = "-14343";
    std::cout<<StringToInt(one)<<std::endl;
    std::cout<<StringToInt(two)<<std::endl;
    return 0;
}

int StringToInt(const char *pstr)
{
    int tempint = 0;
    const char *pt = pstr;
    if(*pt == ‘+‘ || *pt ==‘-‘)
    {
        ++pt;
    }
    while(*pt!=‘\0‘)
    {
        tempint = tempint*10 + (*pt - ‘0‘);
        ++pt; 
    }
    if(*pstr == ‘-‘)
    {
        tempint = -tempint;
    }
    
    return tempint;
    
}