程序员面试金典 - 面试题 16.20. T9键盘（数组）

示例 1:
输入: num = "8733", words = ["tree", "used"]
输出: ["tree", "used"]

示例 2:
输入: num = "2", words = ["a", "b", "c", "d"]
输出: ["a", "b", "c"]

提示：
num.length <= 1000
words.length <= 500
words[i].length == num.length
num中不会出现 0, 1 这两个数字

class Solution {
public:
    vector<string> getValidT9Words(string num, vector<string>& words) {
        string key[10] = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
        vector<string> ans;
        int i;
        bool ok;
        for(auto& w : words)
        {
        	ok = true;
        	for(i = 0; i < w.size(); ++i)
        	{
        		if(key[num[i]-'0'].find(w[i]) == string::npos)
        		{
        			ok = false;
        			break;
        		}
        	}
        	if(ok)
        		ans.push_back(w);
        }
        return ans;
    }
};

class Solution {
public:
    vector<string> getValidT9Words(string num, vector<string>& words) {
        char ch[26] = {'2', '2', '2', '3', '3', '3', '4', '4', '4',
                       '5', '5', '5', '6', '6', '6', '7', '7', '7', '7', 
                       '8', '8', '8', '9', '9', '9', '9'};
        vector<string> ans;
        int i;
        bool ok;
        for(auto& w : words)
        {
        	ok = true;
        	for(i = 0; i < w.size(); ++i)
        	{
        		if(num[i] != ch[w[i]-'a'])
        		{
        			ok = false;
        			break;
        		}
        	}
        	if(ok)
        		ans.push_back(w);
        }
        return ans;
    }
};