题目地址:https://leetcode.com/problems/concatenated-words/
题目描述
Given a list of words (without duplicates), please write a program that returns all concatenated words in the given list of words. A concatenated word is defined as a string that is comprised entirely of at least two shorter words in the given array.
Example:
Input: ["cat","cats","catsdogcats","dog","dogcatsdog","hippopotamuses","rat","ratcatdogcat"]
Output: ["catsdogcats","dogcatsdog","ratcatdogcat"]
Explanation: "catsdogcats" can be concatenated by "cats", "dog" and "cats";
"dogcatsdog" can be concatenated by "dog", "cats" and "dog";
"ratcatdogcat" can be concatenated by "rat", "cat", "dog" and "cat".
Note:
1、 Thenumberofelementsofthegivenarraywillnotexceed10,000;
2、 Thelengthsumofelementsinthegivenarraywillnotexceed600,000.;
3、 Alltheinputstringwillonlyincludelowercaseletters.;
4、 Thereturnedelementsorderdoesnotmatter.;
题目大意
如果有个字符串能够由其他的至少两个字符串拼接构成,那么这个字符串符合要求。问总的有哪些字符串符合要求。
解题方法
动态规划
这个题的解题方法就是139. Word Breakopen in new window,如果不把139搞懂的话,这个题是做不出来的。
方法就是对每个字符串进行一次DP,判断这个字符串是不是能用其他的字符串拼接而成。为了加快判断的速度,使用的是字典保存的字符串。
代码如下:
class Solution {
public:
vector<string> findAllConcatenatedWordsInADict(vector<string>& words) {
if (words.size() <= 2) return {};
unordered_set<string> wordset(words.begin(), words.end());
vector<string> res;
for (string word : words) {
wordset.erase(word);
const int N = word.size();
if (N == 0) continue;
vector<bool> dp(N + 1, false);
dp[0] = true;
for (int i = 0; i <= N; ++i) {
for (int j = 0; j < i; ++j) {
if (dp[j] && wordset.count(word.substr(j, i - j))) {
dp[i] = true;
break;
}
}
}
if (dp.back())
res.push_back(word);
wordset.insert(word);
}
return res;
}
};
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参考资料:http://www.cnblogs.com/grandyang/p/6254527.html
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