LeetCode Java First 400 题解-028

最新推荐文章于 2020-02-16 22:57:17 发布

Felomeng

最新推荐文章于 2020-02-16 22:57:17 发布

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Implement strStr() Easy

Implement strStr().

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

public int strStr(String haystack, String needle) {

    if (haystack == null || needle == null)

        return -1;

    int m = haystack.length();

    int n = needle.length();

    Set<String> ns = new HashSet<String>() {{

        add(needle);

    }};

    for (int i = 0; i < m - n + 1; ++i) {

        String cur = haystack.substring(i, i + n);

        if (ns.contains(cur))

            return i;

    }

    return -1;

}