字符串转换成整数

#include<iostream>
using std::cout;


int func(char *s){
    if(s==NULL) return -1;
    
    int num=0;
    while(*s!=''){
        num = num*10 + *s - '0';//认真体会这条代码 
        ++s;
    }
    
    return num;

}

int main(){
//    char* m = NULL;
    char n[] = "123450";
    cout<<func(n);
    return 0;
}