題目描述

實(shí)現(xiàn)函數(shù) strStr。
函數(shù)聲明如下：
char *strStr(char *haystack, char *needle)

分析

直接匹配

java 代碼

public class Solution {
    public String strStr(String haystack, String needle) {
        if(haystack == null || needle == null || needle.length() ==0){
            return haystack;
        }
        if(haystack.length() < needle.length()){
            return null;
        }
        for(int i = 0; i< haystack.length();i++){
            int j = i;
            int k = 0;
            while(j < haystack.length()&& k < needle.length() &&haystack.charAt(j) == needle.charAt(k)){
                j++;
                k++;                
            }
            if(k >=  needle.length()){
                return haystack.substring(i);
            }
        }
        return null;
    }
}