LeetCode之8，著名的atoi

来源：互联网发布：人工智能与经济学编辑：程序博客网时间：2024/05/21 06:49

（PS：这个题，当初看到的时候，我以为是汉诺塔呢）

原题：

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

注意：考察思维是否全面：0，空格，负数，以及int的最大最小值（最好以16进制）

class Solution {public:    int myAtoi(string str) {        const int maxint=0x7fffffff;        const int minint=0x80000000;                const long long max=0x100000000;        long long ans=0;        bool flag=false;        int st=0;        while(st<str.length() && str[st]==' ')        {         st++;           }        if(st<str.length() && str[st]=='+')         {        st++;        }        else        {        if(st<str.length() && str[st]=='-')        {            flag=true;            st++;        }        }                for(int i=st;i<str.length();i++)        {            if(str[i]<='9' && str[i]>='0')            {                ans=ans*10+str[i]-'0';                if(ans>max) ans=max;             }            else            {                break;            }        }        if(flag) ans=-ans;        if(ans>maxint) ans=maxint;        if(ans<minint) ans=minint;        return ans;    }};

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