Find the Index of the First Occurrence in a String LeetCode Solution

Here, We see Find the Index of the First Occurrence in a String problem Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc., with different approaches.

Find the Index of the First Occurrence in a String LeetCode Solution

Find the Index of the First Occurrence in a String LeetCode Solution

Problem Statement ->

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.

Example 1:
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.

Example 2:
Input: haystack = "leetcode", needle = "leeto"
Output: -1
Explanation: "leeto" did not occur in "leetcode", so we return -1.

Find the Index of the First Occurrence in a String Leetcode Solution C++ ->

class Solution { public: int strStr(string haystack, string needle) { int m = haystack.size(), n = needle.size(); for (int i = 0; i <= m - n; i++) { int j = 0; for (; j < n; j++) { if (haystack[i + j] != needle[j]) { break; } } if (j == n) { return i; } } return -1; } };
Code language: C++ (cpp)

Find the Index of the First Occurrence in a String Leetcode Solution Java ->

class Solution { public int strStr(String haystack, String needle) { int l1 = haystack.length(), l2 = needle.length(); if (l1 < l2) { return -1; } else if (l2 == 0) { return 0; } int threshold = l1 - l2; for (int i = 0; i <= threshold; ++i) { if (haystack.substring(i,i+l2).equals(needle)) { return i; } } return -1; } }
Code language: Java (java)

Find the Index of the First Occurrence in a String Leetcode Solution JavaScript ->

var strStr = function(haystack, needle) { if (needle.length == 0) return 0; for (let i = 0; i < haystack.length; i++) { let k = i, j = 0; while (haystack[k] == needle[j] && j < needle.length) { k++, j++; } if (j == needle.length) return i; } return -1; };
Code language: JavaScript (javascript)

Find the Index of the First Occurrence in a String Leetcode Solution Python ->

class Solution(object): def strStr(self, haystack, needle): for i in range(len(haystack) - len(needle)+1): if haystack[i:i+len(needle)] == needle: return i return -1
Code language: Python (python)