LeetCode 28 : Implement strStr() (Java)

解题思路：扫描。。。时间复杂度O(N*M)。据说最好的算法是KMP算法，不过我还不会。。。

public class Solution {
    public int strStr(String haystack, String needle) {
        if(haystack.length() == 0 && needle.length() == 0) {
            return 0;
        }
        if(haystack.length() < needle.length()) {
            return -1;
        }

        int cur = 0;
        int ind = 0;
        while(ind != haystack.length()) {
            if(cur < needle.length()) {
                if(haystack.charAt(ind) == needle.charAt(cur)) {
                    cur ++;
                    ind ++;
                }
                else if(cur != 0){
                    ind = ind - cur + 1;
                    cur = 0;
                }
                else {
                    ind ++;
                }
            }
            else {
                break;
            }
        }

        if(cur == needle.length()) {
            return ind - cur;
        }
        else {
            return -1;
        }
    }
}