Climbing Stairs
Easy
Determine the number of distinct ways to climb a staircase of n steps by taking either 1 or 2 steps at a time.
Example:
Input: n = 4
Output: 5
Minimum Coin Combination
Medium
You are given an array of coin values and a target amount of money. Return the minimum number of coins needed to total the target amount. If this isn’t possible, return ‐1. You may assume there’s an unlimited supply of each coin.
Example 1:
Input: coins = [1, 2, 3], target = 5
Output: 2
Explanation: Use one 2-dollar coin and one 3-dollar coin to make 5 dollars.
Example 2:
Input: coins = [2, 4], target = 5
Output: -1
Matrix Pathways
Medium
You are positioned at the top-left corner of a m × n matrix, and can only move downward or rightward through the matrix. Determine the number of unique pathways you can take to reach the bottom-right corner of the matrix.
Example:
Input: m = 3, n = 3
Output: 6
Constraints:
m, n ≥ 1
Neighborhood Burglary
Medium
You plan to rob houses in a street where each house stores a certain amount of money. The neighborhood has a security system that sets off an alarm when two adjacent houses are robbed. Return the maximum amount of cash that can be stolen without triggering the alarms.
Example:
Input: houses = [200, 300, 200, 50]
Output: 400
Explanation: Stealing from the houses at indexes 0 and 2 yields 200 + 200 = 400 dollars.
Longest Common Subsequence
Hard
Given two strings, find the length of their longest common subsequence (LCS). A subsequence is a sequence of characters that can be derived from a string by deleting zero or more elements, without changing the order of the remaining elements.
Example:
Input: s1 = 'acabac', s2 = 'aebab'
Output: 3
Longest Palindrome in a String
Medium
Return the longest palindromic substring within a given string.
Example:
Input: s = 'abccbaba'
Output: 'abccba'
Maximum Subarray Sum
Medium
Given an array of integers, return the sum of the subarray with the largest sum.
Example:
Input: nums = [3, 1, -6, 2, -1, 4, -9]
Output: 5
Explanation: subarray [2, -1, 4] has the largest sum of 5.
Constraints:
- The input array contains at least one element.
0/1 Knapsack
Hard
You are a thief planning to rob a store. However, you can only carry a knapsack with a maximum capacity of cap units. Each item (i) in the store has a weight (weights[i]) and a value (values[i]).
Find the maximum total value of items you can carry in your knapsack.
Example:
Input: cap = 7, weights = [5, 3, 4, 1], values = [70, 50, 40, 10]
Output: 90
Explanation: The most valuable combination of items that can fit in the knapsack together are items 1 and 2 . These items have a combined value of 50 + 40 = 90 and a total weight of 3 + 4 = 7 , which fits within the knapsack’s capacity.
Largest Square in a Matrix
Medium
Determine the area of the largest square of 1’s in a binary matrix.
Example:
Output: 9