Leet Code OJ 8. String to Integer (atoi) [Difficulty: Easy]

题目：
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.

翻译：
实现一个atoi函数来把字符串转换为整型变量。

分析：
这道题的AC率只有13.4%，主要是因为对特殊情况的处理上。具体有这么几种情况需要考虑：
1. 前面的空格
2. 除去前面的空格后，可以以“+、-、0”开头，需要做对应的处理
3. 除了起始处可以出现前2种情况提到的非数字字符，其他地方一旦出现，则忽略该字符以及其后的字符
4. 考虑边界，即是否超出Integer.MAX_VALUE，Integer.MIN_VALUE。下面的方案采用long作为临时存储，方便做边界的判断。但是还要考虑是否会超出long的最大值，所以笔者采用length长度做初步判断。

Java版代码（时间复杂度O（n））：

public class Solution {public int myAtoi(String str) {char[] charArr=str.toCharArray();Long result=0L;int startIndex=0;boolean flag=true;//正数int length=0;for(int i=0;i<charArr.length;i++){if(startIndex==i){if(charArr[i]==' '){startIndex++;continue;}if(charArr[i]=='+'||charArr[i]=='0'){continue;}if(charArr[i]=='-'){flag=false;continue;}}if(charArr[i]>='0'&&charArr[i]<='9'){result=result*10+charArr[i]-'0';length++;if(length>10){break;}}else{break;}}if(flag){if(result>Integer.MAX_VALUE){return Integer.MAX_VALUE;}}else{result=-result;if(result<Integer.MIN_VALUE){return Integer.MIN_VALUE;}}return result.intValue();}
}

Leet Code OJ 8. String to Integer (atoi) [Difficulty: Easy]相关推荐

Leet Code OJ 119. Pascal's Triangle II [Difficulty: Easy]
题目: Given an index k, return the kth row of the Pascal's triangle. For example, given k = 3, Return ...
Leet Code OJ 168. Excel Sheet Column Title [Difficulty: Easy]
题目: Given a positive integer, return its corresponding column title as appear in an Excel sheet. For ...
Leet Code OJ 191. Number of 1 Bits [Difficulty: Easy]
题目: Write a function that takes an unsigned integer and returns the number of '1' bits it has (also ...
Leet Code OJ 58. Length of Last Word [Difficulty: Easy]
题目: Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return t ...
Leet Code OJ 171. Excel Sheet Column Number [Difficulty: Easy]
题目: Related to question Excel Sheet Column Title Given a column title as appear in an Excel sheet, r ...
Leet Code OJ 203. Remove Linked List Elements [Difficulty: Easy]
题目: Remove all elements from a linked list of integers that have value val. Example Given: 1 –> 2 ...
Leet Code OJ 328. Odd Even Linked List [Difficulty: Easy]
题目: Given a singly linked list, group all odd nodes together followed by the even nodes. Please note ...
Leet Code OJ 21. Merge Two Sorted Lists [Difficulty: Easy]
题目: Merge two sorted linked lists and return it as a new list. The new list should be made by splici ...
Leet Code OJ 388. Longest Absolute File Path [Difficulty: Medium]
题目 Suppose we abstract our file system by a string in the following manner: The string "dir\n\t ...

Leet Code OJ 8. String to Integer (atoi) [Difficulty: Easy]

Leet Code OJ 8. String to Integer (atoi) [Difficulty: Easy]相关推荐

最新文章

热门文章