【LeetCode】28. Implement strStr()

2024-05-14 22:11:49

Difficulty:easy

More:【目录】LeetCode Java实现

Description

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:

What should we return when needle is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().

Intuition

Use two pointers

Here is a brute-force solution, I will implement KMP algorithm in the future.

Solution

Brute force solution:

    public int strStr(String haystack, String needle) {if(haystack==null || needle==null)return -1;for(int i=0;;i++){for(int j=0;;j++){if(j==needle.length())  return i;if(i+j==haystack.length())  return -1;if(haystack.charAt(i+j)!=needle.charAt(j))    break;}}}

　　

Complexity

Time complexity :

Assume that n = length of haystack and m = length of needle, then the runtime complexity is O(nm).

Space complexity : O(1)

What I've learned

1. It is a great question to ask "What should we return when needle is an empty string?" during an interview.

More:【目录】LeetCode Java实现

转载于:https://www.cnblogs.com/yongh/p/10018767.html

【LeetCode】28. Implement strStr()相关推荐

LeetCode - Easy - 28. Implement strStr()
Topic Two Pointers, String Description https://leetcode.com/problems/implement-strstr/ Implement str ...
【To Do】LeetCode 28. Implement strStr() 和KMP算法
LeetCode 28. Implement strStr() Solution1:我的答案有投机取巧之嫌啊~ 注意string中的查找函数在查找时参考网址:https://www.cnblogs ...
【LeetCode】剑指 Offer 28. 对称的二叉树
[LeetCode]剑指 Offer 28. 对称的二叉树文章目录 [LeetCode]剑指 Offer 28. 对称的二叉树一.递归一.递归对称二叉树定义:对于书中任意两个对称结点 L 和 ...
LeetCode - 28. Implement strStr()
28. Implement strStr() Problem's Link -------------------------------------------------------------- ...
leetCode 28. Implement strStr() 字符串
28. Implement strStr() Implement strStr(). Returns the index of the first occurrence of needle in ha ...
【Leetcode】62. 不同路径
题目一个机器人位于一个 m x n 网格的左上角 (起始点在下图中标记为"Start" ). 机器人每次只能向下或者向右移动一步.机器人试图达到网格的右下角(在下图中标记为&qu ...
【LeetCode】Minimum Depth of Binary Tree 二叉树的最小深度 java
[LeetCode]Minimum Depth of Binary Tree Given a binary tree, find its minimum depth. The minimum dept ...
【LeetCode】309. Best Time to Buy and Sell Stock with Cooldown 最佳买卖股票时机含冷冻期（Medium）（JAVA）
[LeetCode]309. Best Time to Buy and Sell Stock with Cooldown 最佳买卖股票时机含冷冻期(Medium)(JAVA) 题目地址: https: ...
【LeetCode】正则表达式匹配
https://www.imooc.com/article/281353?block_id=tuijian_wz [LeetCode]正则表达式匹配 2019.03.04 19:53 598浏览题目 ...

最新文章

热门文章