500. Keyboard Row

Question:

Given a List of words, return the words that can be typed using letters of alphabet on only one row's of American keyboard like the image below.

Example 1:

Input:["Hello", "Alaska", "Dad", "Peace"]

Output:["Alaska", "Dad"]

Note:

1. You may use one character in the keyboard more than once.
2. You may assume the input string will only contain letters of alphabet.

Solution:

class Solution {
public:
    vector<string> findWords(vector<string>& words) {
        vector<string> result;
        vector<set<char>> v(3);
        string s1 = "QWERTYUIOPqwertyuiop", s2 = "ASDFGHJKLasdfghjkl", s3 = "ZXCVBNMzxcvbnm";
        for (int i = 0; i < s1.length(); i++) v[0].insert(s1[i]);
        for (int i = 0; i < s2.length(); i++) v[1].insert(s2[i]);
        for (int i = 0; i < s3.length(); i++) v[2].insert(s3[i]);
        for (int i = 0; i < words.size(); i++) {
            int tag = -1;
            bool flag = true;
            if (words[i].length() == 0) continue; 
            if (v[0].find(words[i][0]) != v[0].end()) tag = 0;
            if (v[1].find(words[i][0]) != v[1].end()) tag = 1;
            if (v[2].find(words[i][0]) != v[2].end()) tag = 2;
            for (int j = 1; j < words[i].length(); j++) {
                if (v[tag].find(words[i][j]) == v[tag].end()) {
                    flag = false;
                    break;
                }
            }
            if (flag == true)
                result.push_back(words[i]);
        }
        return result;
    }
};

题目直达：https://leetcode.com/problems/keyboard-row/#/description

答案直达：http://www.liuchuo.net/archives/3202