[leetcoide] 【字符串】8. String to Integer (atoi)

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.

Update (2015-02-10):
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题意

将字符串转变为整型数，实现atoi的功能。注意输入的各种情况。

题解

这题没什么难度，就是需要注意几种情况

1、空格符开头的要过滤

2、+、-号开头

3、中间出现非数字字符要中断

4、注意int数的最大最小区间

class Solution {public:    int myAtoi(string str) {        if(str.size()==0)            return 0;        int flag=1;        unsigned int res=0;        int i=0;        while(str[i]==' '&&i<str.size())            i++;        if(str[i]=='-')        {            flag=-1;            i++;        }        else if(str[i]=='+')            i++;        for(;i<str.size();i++)        {            if(str[i]>='0'&&str[i]<='9')            {                int cur=str[i]-'0';                if(res>INT_MAX/10||                                    (res==INT_MAX/10  &&  cur>INT_MAX%10)  )                    return flag==-1 ? INT_MIN : INT_MAX;                                    res=res*10+cur;            }            else break;        }        return res*flag;    }};