判断字符串是否能分割成字典中的单词（一）——Leetcode系列（十一）

最新推荐文章于 2021-06-23 18:50:25 发布

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本文介绍了一个经典的LeetCode问题——单词拆分，并提供了一种使用动态规划的方法来解决该问题。通过递归地检查字符串是否可以由字典中的单词组成。

Word Break

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

For example, given
s = "leetcode",
dict = ["leet", "code"].

Return true because "leetcode" can be segmented as "leet code".

Using dynamic programming to remember if a sub-sentence can be divided into words in dictionary.

My Answer:

public class Solution {
    private Map<String,Boolean> myMap = new HashMap<String,Boolean>();
    public boolean wordBreak(String s, Set<String> dict) {
        // check if the dictionary contains the whole string        
        if (dict.contains(s)) {
            return true;
        }

        // divide the string and check for each substring
        for (int i = 1; i < s.length(); i++) {          

            // check for left half substring
            if (!myMap.containsKey(s.substring(0,i))) {         
                myMap.put(s.substring(0,i), wordBreak(s.substring(0,i), dict));             
            }

            // check for right half substring
            if (!myMap.containsKey(s.substring(i))) {           
                myMap.put(s.substring(i), wordBreak(s.substring(i), dict));             
            }

            // if both substrings are breakable, then the total string is also breakable
            if (myMap.get(s.substring(0,i)) && myMap.get(s.substring(i))) {
                return true;
            }
        }   

        // else the string is not breakable
        return false;       
    }
}

题目来源：https://oj.leetcode.com/problems/word-break/