[leetcode] Implement strStr()

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Implement strStr().

Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

https://oj.leetcode.com/problems/implement-strstr/

思路：目測有BF法，BMP法，BM法等。

 

BF法

public class Solution {public String strStr(String hayStack, String needle) {if (hayStack == null || needle == null)return null;int hayLen = hayStack.length();int neeLen = needle.length();if (hayLen < neeLen)return null;int i, j;int hayStart = 0;while (hayStart <= hayLen-neeLen) {i = hayStart;j = 0;while (i < hayLen && j < neeLen&& hayStack.charAt(i) == needle.charAt(j)) {i++;j++;}if (j == neeLen) {return hayStack.substring(hayStart);}hayStart++;}return null;}public static void main(String[] args) {System.out.println(new Solution().strStr("abcdefg", "cde"));System.out.println(new Solution().strStr("cde", ""));System.out.println(new Solution().strStr("aaabbb", "abbb"));System.out.println(new Solution().strStr("", ""));}}

 

參考：

http://blog.csdn.net/kenden23/article/details/17029625

http://fisherlei.blogspot.com/2012/12/leetcode-implement-strstr.html