Find the Index of the First Occurrence in a String - Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. ... Input: haystack = "sadbutsad", needle = "sad" Output: 0 Explanation: "sad" occurs at index 0 and 6. The first occurrence is at index 0, so we return 0. ... Input: haystack = "leetcode", needle = "leeto" Output: -1 Explanation: "leeto" did not occur in "leetcode", so we return -1.

December 9, 2023 - Time Complexity: O( n * m ) - Where n is the length of haystack and m is the length of needle - Runtime: 0 ms (Beats 100% of Java submissions in LeetCode) - Note: The mentioned time complexity is for worst case scenario. Space Complexity: O( 1 ) - Memory Consumed: 40.5 MB · class Solution { public int strStr(String haystack, String needle) { int hayEnd = haystack.length(); int needEnd = needle.length(); for(int i = 0; i < hayEnd; i++){ while (i < hayEnd && haystack.charAt(i) != needle.charAt(0)) i++; if(i < hayEnd){ int start = i + 1; int needIndex = 1; while(start < hayEnd && needIndex < needEnd && haystack.charAt(start) == needle.charAt(needIndex)){ start++; needIndex++; } if (needIndex == needEnd) return i; } } return -1; } }

LeetCode Solutions in C++23, Java, Python, MySQL, and TypeScript.

August 29, 2024 - class Solution { public: int strStr(string haystack, string needle) { if (needle.empty()) return 0; // If needle is empty, return 0 int n = haystack.length(); int m = needle.length(); for (int i = 0; i <= n - m; i++) { int j = 0; // Check if the substring of haystack starting from i matches needle while (j < m && haystack[i + j] == needle[j]) { j++; } if (j == m) { return i; // Found the first occurrence of needle } } return -1; } }; I tackle LeetCode problems daily and share detailed solutions and approaches on my blog.

In-depth solution and explanation for LeetCode 28. Find the Index of the First Occurrence in a String in Python, Java, C++ and more. Intuitions, example walk through, and complexity analysis. Better than official and forum solutions.

December 26, 2024 - Let’s break it down Find the Index of the First Occurrence in a String and solve it using multiple approaches, including a manual implementation. ... Return the index of the first occurrence of needle in haystack. Return -1 if needle does not exist in haystack. ... Input: haystack = "sadbutsad", needle = "sad" Output: 0 Explanation: "sad" appears first at index 0. ... Input: haystack = "leetcode", needle = "leeto" Output: -1 Explanation: "leeto" is not part of "leetcode".

January 22, 2024 - In summary, the code uses the Knuth-Morris-Pratt algorithm to efficiently search for the first occurrence of a given pattern within a text. The algorithm’s key optimization comes from the use of the Longest Prefix Suffix array, which helps ...

August 11, 2023 - Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. ... Input: haystack = "sadbutsad", needle = "sad" Output: 0 Explanation: "sad" occurs at index 0 and 6. The first occurrence is at index 0, so we return 0. ... Input: haystack = "leetcode", needle = "leeto" Output: -1 Explanation: "leeto" did not occur in "leetcode", so we return -1.

March 1, 2025 - Efficient way of solving this is using Knuth–Morris–Pratt (KMP) Algorithm · Templates let you quickly answer FAQs or store snippets for re-use

August 4, 2025 - Should handle empty needle (LeetCode requires returning 0). Should handle empty haystack gracefully. ... public int StrStr(string haystack, string needle) { return haystack.IndexOf(needle, StringComparison.Ordinal); }

December 28, 2025 - class Solution { public int strStr(String haystack, String needle) { int n1 = haystack.length(); int n2 = needle.length(); if (n2 == 0) { return -1; } for (int i = 0; i <= n1 - n2; i++) { if (haystack.charAt(i) == needle.charAt(0)) { if (compare(haystack, needle, i)) { return i; } } } return -1; } private boolean compare(String haystack, String needle, int idx) { int n1 = haystack.length(); int n2 = needle.length(); if (idx + n2 > n1) { return false; } for (int i = 0; i < n2; i++) { if (needle.charAt(i) != haystack.charAt(idx + i)) { return false; } } return true; } } ... #leetcode #programming #ai #beginners 151.

March 3, 2023 - Leetcode 28. Find the Index of the First Occurrence in a String ( leetcode daily challenge, march 2023). Here is a python solution with an easy explanation.

October 5, 2024 - import java.util.*; public class Solution { public int strStr(String haystack, String needle) { // If needle is empty, return 0 as per convention if (needle.isEmpty()) { return 0; } // Use indexOf to find the starting index of needle in haystack return haystack.indexOf(needle); } public static void main(String args[]) { Scanner sc= new Scanner(System.in); System.out.print("Enter the substring that that you wanted to search in the main string:-\t"); String needle=sc.nextLine(); System.out.println("Enter the word among who the substrings existence is to be found:-\t"); String haystack=sc.nextLine(); int startIndex=haystack.indexOf(needle); if (startIndex!=-1){ System.out.println(startIndex); }else{ System.out.println(startIndex); } } }

August 21, 2025 - class Solution { public int strStr(String haystack, String needle) { for (int i = 0; i <= haystack.length() - needle.length(); i++) { if (haystack.substring(i, i + needle.length()).equals(needle)) { return i; } } return -1; } } ... LeetCode #206.