字符串与整数之间的转换

void main(){
    char str[18] ="t88355";
    int num = atoi(str+1);
    //把字符串转换成整数,参数传递的是从某一位开始往后的所有字符，出现非数字字符都会转换失败，就是0
    printf("%d\n",num); //  88355

}

 

//字符串与整数之间的转换
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int getTen(int n){
    int res = 1;
    for (int i = 1; i <= n; ++i) {
        res *= 10;
    }
    return res;
}
int toNum(char *str){
    int res =0;
    int length  = strlen(str);

    while(*str != '\0'){
        if(*str <= '9' && *str >= '0'){
            res += getTen(length -1 ) * (*str - 48);  //字符转为相应的数字就减去48 也就是’0‘的ASCII码
        } else{
            return  -1;
        }
        str++;
        length--;
    }
    return  res;
}

char * toString(int *pInt){
    //char str[20] ={'\0'};
    int num = *pInt;
    //计算有多少位
    int i=0;
    do{
        i++;
    }while (num = num / 10);
    char *str = (char *) calloc(i+1, sizeof(char));  //多余的一个字符空间默认会置为 '0'
    num = *pInt;
    int bit =0;
    for (int j = i -1; j >=0 ; --j) {
        bit = num % 10;
        num = num / 10;
        str[j] = bit +48;
    }
    return str;
}

void main(){
    char *str = "1255634";
    int num = 1234;
    int *pInt =#
    printf("%d\n",toNum(str));
    printf("%s\n",toString(&num));
}