# Evaluate Reverse Polish Notation (Leetcode 150)

Difficulty: Medium Link: Day 25: May Leetcode Challenge Problem Description Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, and /. Each…

# Find Duplicate File in System (Leetcode 609)

Difficulty: Medium Link: Day 18: May Leetcode Challenge Problem Description Given a list paths of directory info, including the directory path, and all the files with contents…

# Longest String Chain (Leetcode 1048)

Difficulty: Medium Link: Day 17: May Leetcode Challenge Problem Description Given a list of words, each word consists of English lowercase letters. Let’s say word1 is a…

# Ambiguous Coordinates (Leetcode 816)

Difficulty: Medium Link: Day 13: May Leetcode Challenge Problem Description We had some 2-dimensional coordinates, like “(1, 3)” or “(2, 0.5)”.  Then, we removed all commas, decimal points, and…

# Interval List Intersections (Leetcode 986)

Difficulty: Medium Link: Leetcode 986 Problem Statement You are given two lists of closed intervals, firstList and secondList, where firstList[i] = [starti, endi] and secondList[j] = [startj, endj]. Each list of…

# Delete Operation for Two Strings (Leetcode 583)

Problem Description Given two strings word1 and word2, return the minimum number of steps required to make word1 and word2 the same. In one step, you can delete exactly one character in either string. Examples Constraints…

# Convert Sorted List to Binary Search Tree (Leetcode 109)

Difficulty: Medium. Link: Day 6: May Leetcode Challenge Problem Description Given the head of a singly linked list where elements are sorted in ascending order, convert it to…

# Jump Game II (Leetcode 45)

Difficulty: Medium Link : Day 5: May Leetcode Challenge Problem Description Given an array of non-negative integers nums, you are initially positioned at the first index…

# Non-decreasing Array (Leetcode 665)

Difficulty: Medium Link: Day 4 : May Leetcode Challenge Problem Description Given an array nums with n integers, your task is to check if it could become non-decreasing by…

# Running Sum of 1d Array (Leetcode 1480)

Difficulty: Easy Link: Day 3: May Leetcode Challenge Problem Statement Given an array nums. We define a running sum of an array as runningSum[i] = sum(nums[0]…nums[i]). Return…