问题链接

Implement strStr() | LeetCode OJ

问题描述

实现字符串查找函数，给出两个字符串haystack和needle，返回needle在haystack中的第一次出现的位置，不存在则返回-1。

解决办法

public class Solution {
    public int strStr(String haystack, String needle) {
        int haystackLength = haystack.length();
        int needleLength = needle.length();
        if(haystackLength == 0 && needleLength == 0){
            return 0;
        }
        else if(haystackLength == 0){
            return -1;
        }
        else if(needleLength == 0){
            return 0;
        }
        else if(haystackLength < needleLength){
            return -1;
        }
        int startPosition = haystackLength - needleLength;
        for (int i = 0; i <= startPosition; i++) {
            boolean same = true;
            for (int j = 0; j < needleLength; j++) {
                char a = haystack.charAt(i + j);
                char b = needle.charAt(j);
                if (a != b) {
                    same = false;
                    break;
                }
            }
            if (same) {
                return i;
            }
        }
        return -1;
    }
}