Skip to main content

16. Word Break

mediumAsked at Chime

Determine if a string can be segmented into a space-separated sequence of dictionary words.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

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. The same dictionary word may be reused multiple times.

Constraints

  • 1 <= s.length <= 300
  • 1 <= wordDict.length <= 1000
  • All strings consist of lowercase English letters.

Examples

Example 1

Input
s = "leetcode", wordDict = ["leet","code"]
Output
true

Example 2

Input
s = "applepenapple", wordDict = ["apple","pen"]
Output
true

Approaches

1. Naive recursion

Try every prefix that is in the dictionary and recurse on the suffix.

Time
O(2^n)
Space
O(n)
function can(s) {
  if (s === '') return true;
  for (const w of wordDict) {
    if (s.startsWith(w) && can(s.slice(w.length))) return true;
  }
  return false;
}

Tradeoff:

2. Bottom-up DP

Let dp[i] mean s[0..i) can be segmented. Transition: dp[i] = exists j < i where dp[j] is true and s[j..i) is in the dictionary set.

Time
O(n^2)
Space
O(n)
function wordBreak(s, wordDict) {
  const set = new Set(wordDict);
  const dp = new Array(s.length + 1).fill(false);
  dp[0] = true;
  for (let i = 1; i <= s.length; i++) {
    for (let j = 0; j < i; j++) {
      if (dp[j] && set.has(s.slice(j, i))) {
        dp[i] = true;
        break;
      }
    }
  }
  return dp[s.length];
}

Tradeoff:

Chime-specific tips

Chime treats word-break-style segmentation as a stand-in for parsing transaction memos in their fraud heuristics pipeline, so mention how memoization avoids re-scoring the same memo prefix.

Solve it now

Free. No sign-up. Python and JavaScript run instantly in your browser.

Output

Press Run or Cmd+Enter to execute

Practice these live with InterviewChamp.AI

Drill Word Break and other Chime interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →