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;

    

}