LeetCode : String to Integer (atoi) [java]

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最新推荐文章于 2022-07-27 16:48:14 发布

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分类专栏： Java 编程练习题文章标签： LeetCode String to Integer at

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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.

思路：考虑前后空格，正负号，为空等输入情况，考虑溢出，使用long类型判断当前值是否已经溢出。

public class Solution {
    public int myAtoi(String str) {
		if (str == null || str.equals("")) {
			return 0;
		}
		String myStr = str.trim();
		int max = Integer.MAX_VALUE;
		int min = Integer.MIN_VALUE;
		long result = 0;
		int isPositive = 1;
		int index = 0;
		char begin = myStr.charAt(0);
		if (begin == '-') {
			isPositive = -1;
			index = 1;
		}
		if(begin == '+'){
		    index = 1;
		}
		for (int i = index; i < myStr.length(); i++) {
			char ch = myStr.charAt(i);
			if (ch > '9' || ch < '0') {
				return (int) result * isPositive;
			} else {
				result = result * 10 + ch - '0';
				if (result > max || result < min) {
					return isPositive == 1 ? max : min;
				}
			}
		}
		return (int) result * isPositive;
    }
}