## Remove K Digits

Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible. Note: The length of num is less than 10002 and will be ≥ k. The given num does not contain any leading zero. Example 1: Input: num = "1432219", k = 3 Output: "1219" Explanation: Remove the three digits 4, 3, and 2 to form the new number 1219 which is the smallest.

by lek tin in "algorithm" access_time 2-min read

## Jump Game II

Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position. Your goal is to reach the last index in the minimum number of jumps. Example: Input: [2,3,1,1,4] Output: 2 Explanation: The minimum number of jumps to reach the last index is 2. Jump 1 step from index 0 to 1, then 3 steps to the last index.

by lek tin in "algorithm" access_time 1-min read

## Jump Game

Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position. Determine if you are able to reach the last index. Example 1 Input: [2,3,1,1,4] Output: true Explanation: Jump 1 step from index 0 to 1, then 3 steps to the last index. Example 2 Input: [3,2,1,0,4] Output: false Explanation: You will always arrive at index 3 no matter what.

by lek tin in "algorithm" access_time 1-min read

## Valid Parenthesis String

Given a string containing only three types of characters: '(', ')' and '*', write a function to check whether this string is valid. We define the validity of a string by these rules: Any left parenthesis '(' must have a corresponding right parenthesis ')'. Any right parenthesis ')' must have a corresponding left parenthesis '('. Left parenthesis '(' must go before the corresponding right parenthesis ')'. '*' could be treated as a single right parenthesis ‘)’ or a single left parenthesis '(' or an empty string.

by lek tin in "algorithm" access_time 1-min read

## Minimum Number of Refueling Stops

A car travels from a starting position to a destination which is target miles east of the starting position. Along the way, there are gas stations. Each station[i] represents a gas station that is station[i][0] miles east of the starting position, and has station[i][1] liters of gas. The car starts with an infinite tank of gas, which initially has startFuel liters of fuel in it. It uses 1 liter of gas per 1 mile that it drives.

by lek tin in "algorithm" access_time 3-min read

## Split Array Into Consecutive Subsequences

Given an array nums sorted in ascending order, return true if and only if you can split it into 1 or more subsequences such that each subsequence consists of consecutive integers and has length at least 3. Example 1 Input: [1,2,3,3,4,5] Output: True Explanation: You can split them into two consecutive subsequences : 1, 2, 3 3, 4, 5 Example 2 Input: [1,2,3,3,4,4,5,5] Output: True Explanation: You can split them into two consecutive subsequences : 1, 2, 3, 4, 5 3, 4, 5 Example 3 Input: [1,2,3,4,4,5] Output: False Constraints 1 <= nums.

by lek tin in "algorithm" access_time 2-min read

## Validate Stack Sequence

Given two sequences pushed and popped with distinct values, return true if and only if this could have been the result of a sequence of push and pop operations on an initially empty stack. Example 1 Input: pushed = [1,2,3,4,5], popped = [4,5,3,2,1] Output: true Explanation: We might do the following sequence: push(1), push(2), push(3), push(4), pop() -> 4, push(5), pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1 Example 2 Input: pushed = [1,2,3,4,5], popped = [4,3,5,1,2] Output: false Explanation: 1 cannot be popped before 2.

by lek tin in "algorithm" access_time 1-min read

## Remove Duplicate Letters

Given a string which contains only lowercase letters, remove duplicate letters so that every letter appears once and only once. You must make sure your result is the smallest in lexicographical order among all possible results. Example 1 Input: "bcabc" Output: "abc" Example 2 Input: "cbacdcbc" Output: "acdb" Example 3 Input: "cba" Output: "cba" Solution class Solution: def removeDuplicateLetters(self, s: str) -> str: stack = [] seen = set() last_indices = {c: i for i, c in enumerate(s)} for i, c in enumerate(s): print(c, seen, stack) if c not in seen: while stack and c < stack[-1] and i < last_indices[stack[-1]]: seen.

by lek tin in "algorithm" access_time 1-min read

## Candy

There are N children standing in a line. Each child is assigned a rating value. You are giving candies to these children subjected to the following requirements: Each child must have at least one candy. Children with a higher rating get more candies than their neighbors. What is the minimum candies you must give? Example 1 Input: [1,0,2] Output: 5 Explanation: You can allocate to the first, second and third child with 2, 1, 2 candies respectively.

by lek tin in "algorithm" access_time 1-min read

## Bag of Tokens

You have an initial power P, an initial score of 0 points, and a bag of tokens. Each token can be used at most once, has a value token[i], and has potentially two ways to use it. If we have at least token[i] power, we may play the token face up, losing token[i] power, and gaining 1 point. If we have at least 1 point, we may play the token face down, gaining token[i] power, and losing 1 point.

by lek tin in "algorithm" access_time 1-min read