387. First Unique Character in a String
2016-09-06 20:23
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题目:First Unique Character in a String
原题链接:https://leetcode.com/problems/first-unique-character-in-a-string/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.
找出一个字符串(只含小写字母)中第一个不重复的字符,并返回它的下标。
例:
s = “leetcode”
return 0.( l 是第一个不重复的字符)
s = “loveleetcode”,
return 2.( v 是第一个不重复的字符)
用一个数组hash来统计字符串中每个小写字母出现的次数,然后重新扫描一遍字符串,第一个出现次数为 1 的就返回它的下标,如果没有满足要求的,就返回 -1 .
代码如下:
class Solution { public: int firstUniqChar(string s) { int hash[26]; fill(hash, hash + 26, -1); for(auto str : s) hash[(str - 'a')] ++; int len = s.length(); for(int i = 0; i < len; ++i) { if(hash[(s[i] - 'a')] == 0) return i; } return -1; } };
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