面试题 01.04. Palindrome Permutation LCCI

Problem

Given a string, write a function to check if it is a permutation of a palin­ drome. A palindrome is a word or phrase that is the same forwards and backwards. A permutation is a rearrangement of letters. The palindrome does not need to be limited to just dictionary words.

Example

Input: “tactcoa”
Output: true（permutations: “tacocat”、“atcocta”, etc.）

Solution

回文中，最多只有一个字符的个数是奇数。

class Solution {
public:
    bool canPermutePalindrome(string s) {
        unordered_map<char,int> hash_table;
        for(auto c:s)
        {
            hash_table[c]++;
        }

        int odd_cnt = 0;
        for(unordered_map<char,int>::const_iterator it = hash_table.begin();
        it != hash_table.end();++it)
        {
            if(it->second % 2 == 1)
            {
                ++odd_cnt;
                if(odd_cnt > 1)
                {
                    return false;
                }
            }
        }

        return true;

    }
};