字符串转换为整数

#include<iostream>#include<string>#include<assert.h>using namespace std;int str_2_int(string str){assert(str.size()>0);int pos = 0;int sym = 1;if(str[pos] == '+')pos++;else if(str[pos] == '-'){pos++;sym=-1;}int num =0;while(pos<str.length()){assert(str[pos]>='0');assert(str[pos]<='9');num = num*10+(str[pos]-'0');assert(num>=0);pos++;}num*=sym;return num;}int main(){string str = "-1024";int num = str_2_int(str);cout << num << endl;return 0;}