go语言LeetCode题解720词典中最长的单词

输入：words = ["w","wo","wor","worl", "world"]
输出："world"
解释： 单词"world"可由"w", "wo", "wor", 和 "worl"逐步添加一个字母组成。

输入：words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
输出："apple"
解释："apply" 和 "apple" 都能由词典中的单词组成。但是 "apple" 的字典序小于 "apply" 

class Solution {
public:
    string longestWord(vector<string>& words) {
        if( words.size() == 0 ){
            return NULL;
        }
		unordered_map<string, int> hashWord;
		for( auto& hw : words ){
			++hashWord[hw];
		}
		int maxLength = 0;
		string word = "";
		for( auto& w : words ){
			if( maxLength < w.length() ){
				bool cntFlag = false;
				string strW = "";
				for( int i = 0; i < w.length(); ++i ){
					strW += w[i];
					if( !hashWord.count( strW ) ){
						cntFlag = true;
						break;
					}
				}
				if( !cntFlag ){
					word = "";
					word = w;
					maxLength = w.length();
				}
			}else if( maxLength == w.length() ){
				bool cntFlag = false;
				string strW = "";
				for( int i = 0; i < maxLength; ++i ){
					strW += w[i];
					cout << strW << endl;
					if( !hashWord.count( strW ) ){
						cntFlag = true;
						break;
					}
				}
				if( !cntFlag ){
					for( int i = 0; i < maxLength; ++i ){
						if( word[i] < w[i] ){
							break;
						}else if( word[i] > w[i] ){
							word = "";
							word = w;
						}
					}
				}
			}
		}
		return word;
    }
};