Word Break

Problem

Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a space-separated sequence of one or more dictionary words.

Note that the same word in the dictionary may be reused multiple times in the segmentation.

 

Example 1:

**Input:** s = "leetcode", wordDict = ["leet","code"]
**Output:** true
**Explanation:** Return true because "leetcode" can be segmented as "leet code".

Example 2:

**Input:** s = "applepenapple", wordDict = ["apple","pen"]
**Output:** true
**Explanation:** Return true because "applepenapple" can be segmented as "apple pen apple".
Note that you are allowed to reuse a dictionary word.

Example 3:

**Input:** s = "catsandog", wordDict = ["cats","dog","sand","and","cat"]
**Output:** false

 

Constraints:

• 1 <= s.length <= 300
• 1 <= wordDict.length <= 1000
• 1 <= wordDict[i].length <= 20
• s and wordDict[i] consist of only lowercase English letters.
• All the strings of wordDict are unique.

Code

✅ Javascript

Solution

题目含义：判断字符串是否能用字典中给到的单词组成

解题思路：

• 动态规划解题，dp[s[i 到 j]] = true，则dp[n]及為true。

var wordBreak = function (s, wordDict) {
    let n = s.length, dp = new Array(n + 1).fill(false), words = new Set(wordDict)
    dp[0] = true
    for (let i = 1; i <= n; i++) {
        for (let j = 0; j < i; j++) {
            if (dp[j] && words.has(s.substring(j, i))) {
                dp[i] = true
                break
            }
        }
    }
    return dp[n]
};

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