Word Break

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Word Break

Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

Solution1

DP

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public boolean wordBreak(String s, List<String> wordDict) {
    int length = s.length();
    if (length == 0 || s == null || wordDict == null) {
        return false;
    }

    boolean[] dp = new boolean[length + 1];
    dp[0] = true;

    for (int i = 1; i <= length; i++) {
        for (int j = 0; j < i; j++) {
            String tmp = s.substring(j, i);
            if (dp[j] && wordDict.contains(tmp)) {
                dp[i] = true;
                break;
            }
        }
    }
    return dp[length];
}

BFS 

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public boolean wordBreak(String s, List<String> wordDict) {
    int length = s.length();
    if (length == 0 || s == null || wordDict == null) {
        return false;
    }
    
    Queue<Integer> queue = new LinkedList<>();
    Set<Integer> visited = new HashSet<>();
    queue.offer(0);
    visited.add(0);

    while (!queue.isEmpty()) {
        int currentIndex = queue.poll();
        for (int i = currentIndex + 1; i <= length; i++) {
            if (visited.contains(i)) {
                continue;
            }
            if (wordDict.contains(s.substring(currentIndex, i))) {
                if (i == length) {
                    return true;
                }
                queue.offer(i);
                visited.add(i);
            }
        }
    }
    return false;
}