LeetCode-String to Integer (atoi) -解題報告

原題鏈接 https://leetcode.com/problems/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. 

實現atoi的功能。

我就說一下有一些注意的地方。

1. 字符串開始可能有空白符需要跳過。
2. 正負數的情況。
3. 數值超過了int的表示範圍

class Solution {
public:
    int myAtoi(string str) {
		int pos = 0;
		long long ans = 0;
		bool sign = true;

		while (str[pos] == ' ')pos++;
		if (str[pos] == '-')sign = false, pos++;
		else if(str[pos] == '+')pos++;

		while (pos < str.length())
		{
			int tmp = str[pos] - '0';
			if(tmp >= 0 && tmp <= 9)ans = ans * 10 + tmp;
			else break;
			if (ans > INT_MAX || ans < INT_MIN)return sign ? INT_MAX : INT_MIN;
			pos++;
		}
		return sign ? ans : -ans;
	}
};