LeetCode 28. Implement strStr()

题目描述

Implement strStr().

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

Example 1:

Input: haystack = "hello", needle = "ll"
Output: 2

Example 2:

Input: haystack = "aaaaa", needle = "bba"
Output: -1

Clarification:
we will return 0 when needle is an empty string.

题目思路

代码 C++

• 思路一、

class Solution {
public:
    int strStr(string haystack, string needle) {
        if(needle == ""){
            return 0;
        }
        
        int a1 = haystack.size();
        int a2 = needle.size();
        int k, tt;
        
        for(int i=0; i < a1; i++){
            k = i;
            tt = 0;
            for(int j=0; j < a2 && k < a1 ; j++){
                if(haystack[k] == needle[j]){
                    tt = tt + 1;
                    k = k + 1;
                }
                else{
                    break; // 跳出内层 for 循环
                }
            }
            
            if(tt == a2){
                return i;
            }
        }
        return -1;
    }
};

• 思路二、

总结展望