#include<stdio.h>

#include<iostream>

using namespace std;

int myatoi(char *str){

    if(NULL == str)return ;//处理空指针,加强程序的鲁棒性

    int sight=,ret=,i=;

    while(str[i]==' ')i++;//处理字符串开始的空格

    if(str[i]=='+'||str[i]=='-'){ //处理正负号

        if(str[i]=='-')sight=-;

        i++;

    }

    for(;str[i]>=''&&str[i]<='';i++){

        ret*=;

        ret+=str[i]-'';

        if(ret<){//溢出控制

            return ;

        }

    }

    return ret*sight;

}

int main(){

    char *s=NULL;

    printf("%d\n",myatoi(s));

    printf("%d\n",myatoi("   -123189267q    2e.1"));

    getchar();

    return ;

}