如何加快第一个唯一字符查找

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是否有一些技巧可以提高LeetCode得分？似乎增强型 for-each 循环的性能比标准 for 循环要好，但我无法证明这一点，

解决方案

我得到 98.58 ％的内容是：-

public int firstUniqChar（String s）{ int count [] = new int [122-96]; final char [] chars = s.toCharArray（）; for（int i = 0; i< chars.length; i ++）{ count [chars [i]-97] ++; } for（int i = 0; i< chars.length; i ++）{ if（count [chars [i]-97] == 1）返回一世; } 返回-1； }

I'm solving 387. First Unique Character in a String LeetCode problem defined as:

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode" return 0. s = "loveleetcode", return 2.

Note: You may assume the string contain only lowercase letters.

Taking advantage of the input being fully lowercase ASCII I created two bit vectors to track when we encounter a character for the first and second time.

Can below code be improved further? LeetCode says that below code is better than 94.33% solutions. What else could have been done by the last 5.67% solutions that they were better?

class Solution { public int firstUniqChar(String s) { int firstSpot = 0; int secondSpot = 0; char[] chars = s.toCharArray(); for (char c : chars) { int mask = 1 << c - 'a'; if ((firstSpot & mask) == 0) { firstSpot |= mask; } else if ((secondSpot & mask) == 0) { secondSpot |= mask; } } int i = 0; for (char c : chars) { int mask = 1 << c - 'a'; if ((secondSpot & mask) == 0) { return i; } i++; } return -1; } }

Are there tricks that can be done to improve the LeetCode score? It seems that enhanced for-each loop performs better than standard for loop but I can't prove it, It's an observation based on few of my previous submissions.

解决方案

I got 98.58% with this:-

public int firstUniqChar(String s) { int count[] = new int[122 - 96]; final char[] chars = s.toCharArray(); for (int i = 0; i < chars.length; i++) { count[chars[i] - 97]++; } for (int i = 0; i < chars.length; i++) { if (count[chars[i] - 97] == 1) return i; } return -1; }