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leetcode solution
  • Leetcode Solutions
  • LeetCode 1. Two Sum
  • LeetCode 2. Add Two Numbers
  • LeetCode 3. Longest Substring Without Repeating Characters
  • LeetCode 4. Median of Two Sorted Arrays
  • LeetCode 5. Longest Palindromic Substring
  • LeetCode 6. ZigZag Conversion
  • LeetCode 7. Reverse Integer
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  • LeetCode 9. Palindrome Number
  • LeetCode 10. Regular Expression Matching
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  • LeetCode 13. Roman to Integer
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  • LeetCode 17. Letter Combinations of a Phone Number
  • LeetCode 18. 4Sum
  • LeetCode 19. Remove Nth Node From End of List
  • LeetCode 20. Valid Parentheses
  • LeetCode 21. Merge Two Sorted Lists
  • LeetCode 22. Generate Parentheses
  • LeetCode 23. Merge k Sorted Lists
  • LeetCode 24. Swap Nodes in Pairs
  • LeetCode 25. Reverse Nodes in k-Group
  • LeetCode 26. Remove Duplicates from Sorted Array
  • LeetCode 27. Remove Element
  • LeetCode 28. Implement strStr()
  • LeetCode 29. Divide Two Integers
  • LeetCode 30. Substring with Concatenation of All Words
  • LeetCode 31. Next Permutation
  • LeetCode 32. Longest Valid Parentheses
  • LeetCode 33. Search in Rotated Sorted Array
  • LeetCode 42. Trapping Rain Water
  • LeetCode 56. Merge Intervals
  • LeetCode 67. Add Binary
  • LeetCode 81. Search in Rotated Sorted Array II
  • LeetCode 124. Binary Tree Maximum Path Sum
  • LeetCode 125. Valid Palindrome
  • LeetCode 153. Find Minimum in Rotated Sorted Array
  • LeetCode 154. Find Minimum in Rotated Sorted Array II
  • LeetCode 157. Read N Characters Given Read4
  • LeetCode 158. Read N Characters Given Read4 II - Call multiple times
  • LeetCode 236. Lowest Common Ancestor of a Binary Tree
  • LeetCode 238. Product of Array Except Self
  • LeetCode 269. Alien Dictionary
  • Leetcode 295. Find Median from Data Stream
  • Leetcode 297. Serialize and Deserialize Binary Tree
  • LeetCode 300. Longest Increasing Subsequence
  • LeetCode 301. Remove Invalid Parentheses
  • LeetCode 336. Palindrome Pairs
  • LeetCode 407. Trapping Rain Water II
  • LeetCode 415. Add Strings
  • LeetCode 426. Convert Binary Search Tree to Sorted Doubly Linked List
  • LeetCode 489. Robot Room Cleaner
  • LeetCode 560. Subarray Sum Equals K
  • LeetCode 680. Valid Palindrome II
  • LeetCode 710. Random Pick with Blacklist
  • LeetCode 721. Accounts Merge
  • LeetCode 863. All Nodes Distance K in Binary Tree
  • LeetCode 918. Maximum Sum Circular Subarray
  • LeetCode 953. Verifying an Alien Dictionary
  • LeetCode 973. K Closest Points to Origin
  • LeetCode 1249. Minimum Remove to Make Valid Parentheses
  • LeetCode 1428. Leftmost Column with at Least a One
  • LeetCode 1570. Dot Product of Two Sparse Vectors
  • LeetCode 1644. Lowest Common Ancestor of a Binary Tree II
  • LeetCode 1650. Lowest Common Ancestor of a Binary Tree III
  • LeetCode 1676. Lowest Common Ancestor of a Binary Tree IV
  • Leetcode 1727. Largest Submatrix With Rearrangements
  • LeetCode 1751. Maximum Number of Events That Can Be Attended II
  • LeetCode 1754. Largest Merge Of Two Strings
  • LeetCode 1755. Closest Subsequence Sum
  • LeetCode 1760. Minimum Limit of Balls in a Bag
  • LeetCode 1761. Minimum Degree of a Connected Trio in a Graph
  • LeetCode 1764. Form Array by Concatenating Subarrays of Another Array
  • LeetCode 1765. Map of Highest Peak
  • LeetCode 1766. Tree of Coprimes
  • LeetCode 1770. Maximum Score from Performing Multiplication Operations
  • LeetCode 1771. Maximize Palindrome Length From Subsequences
  • LeetCode 1774. Closest Dessert Cost
  • LeetCode. 1775 Equal Sum Arrays With Minimum Number of Operations
  • LeetCode 1776. Car Fleet II
  • LeetCode 1778. Shortest Path in a Hidden Grid
  • LeetCode 1779. Find Nearest Point That Has the Same X or Y Coordinate
  • LeetCode 1780. Check if Number is a Sum of Powers of Three
  • LeetCode 1781. Sum of Beauty of All Substrings
  • LeetCode 1782. Count Pairs Of Nodes
  • LeetCode 1784. Check if Binary String Has at Most One Segment of Ones
  • LeetCode 1785. Minimum Elements to Add to Form a Given Sum
  • LeetCode 1786. Number of Restricted Paths From First to Last Node
  • LeetCode 1787. Make the XOR of All Segments Equal to Zero
  • LeetCode 1788. Maximize the Beauty of the Garden
  • LeetCode 1790. Check if One String Swap Can Make Strings Equal
  • LeetCode 1791. Find Center of Star Graph
  • LeetCode 1792. Maximum Average Pass Ratio
  • LeetCode 1793. Maximum Score of a Good Subarray
  • LeetCode 1794. Count Pairs of Equal Substrings With Minimum Difference
  • LeetCode 1796. Second Largest Digit in a String
  • LeetCode 1797. Design Authentication Manager
  • LeetCode 1798. Maximum Number of Consecutive Values You Can Make
  • LeetCode 1799. Maximize Score After N Operations
  • LeetCode 1800. Maximum Ascending Subarray Sum
  • LeetCode 1801. Number of Orders in the Backlog
  • LeetCode 1802. Maximum Value at a Given Index in a Bounded Array
  • LeetCode 1803. Count Pairs With XOR in a Range
  • LeetCode 1804. Implement Trie II (Prefix Tree)
  • LeetCode 1805. Number of Different Integers in a String
  • LeetCode 1807. Evaluate the Bracket Pairs of a String
  • LeetCode 1808. Maximize Number of Nice Divisors
  • LeetCode 1810. Minimum Path Cost in a Hidden Grid
  • LeetCode 1812. Determine Color of a Chessboard Square
  • LeetCode 1813. Sentence Similarity III
  • LeetCode 1814. Count Nice Pairs in an Array
  • LeetCode 1815. Maximum Number of Groups Getting Fresh Donuts
  • LeetCode 1816. Truncate Sentence
  • LeetCode 1817. Finding the Users Active Minutes
  • LeetCode 1818. Minimum Absolute Sum Difference
  • LeetCode 1819. Number of Different Subsequences GCDs
  • LeetCode 1820. Maximum Number of Accepted Invitations
  • LeetCode 1822. Sign of the Product of an Array
  • LeetCode 1824. Minimum Sideway Jumps
  • LeetCode 1825. Finding MK Average
  • LeetCode 1826. Faulty Sensor
  • LeetCode 1827. Minimum Operations to Make the Array Increasing
  • LeetCode 1828. Queries on Number of Points Inside a Circle
  • LeetCode 1829. Maximum XOR for Each Query
  • LeetCode 1830. Minimum Number of Operations to Make String Sorted
  • LeetCode 1832. Check if the Sentence Is Pangram
  • LeetCode 1833. Maximum Ice Cream Bars
  • LeetCode 1834. Single-Threaded CPU
  • LeetCode 1835. Find XOR Sum of All Pairs Bitwise AND
  • LeetCode 1836. Remove Duplicates From an Unsorted Linked List
  • LeetCode 1837. Sum of Digits in Base K
  • LeetCode 1839. Longest Substring Of All Vowels in Order
  • LeetCode 1840. Maximum Building Height
  • LeetCode 1847. Closest Room
  • LeetCode 1850. Minimum Adjacent Swaps to Reach the Kth Smallest Number
  • LeetCode 1851. Minimum Interval to Include Each Query
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LeetCode 28. Implement strStr()

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Last updated 4 years ago

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Implement .

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

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 and Java's .

Example 1:

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

Example 2:

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

Example 3:

Input: haystack = "", needle = ""
Output: 0

Constraints:

  • 0 <= haystack.length, needle.length <= 5 * 10^4

  • haystack and needle consist of only lower-case English characters.

Solution:

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

strStr()
strstr()
indexOf()
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