第45题 Implement strStr()

原创于 2015-01-26 16:47:13 发布 · 533 阅读

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本文介绍了一种在Java中实现strStr()函数的方法，该函数返回字符串haystack中首次出现needle的位置索引，若needle不是haystack的子串则返回-1。提供了详细的代码示例，并提到了KMP、BM和Sunday等高级搜索算法。

Implement strStr().

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

Update (2014-11-02):
The signature of the function had been updated to return the index instead of the pointer. If you still see your function signature returns a char * or String, please click the reload button to reset your code definition.

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Solution in Java：

public class Solution {
    public int strStr(String haystack, String needle) {
        char[] hay = haystack.toCharArray();
        char[] need = needle.toCharArray();
        for(int i=0; i<hay.length-need.length+1; i++){
            int index = 0; 
            while(index<need.length&&hay[i+index]==need[index]) index++;
            if(index==need.length) return i;
        }
        return -1;
    }
}

KMP，BM，Sunday算法待研究！