LeetCode 39xx

LeetCode problems 3900–3999

38 items

LeetCode 39xx

# Problem Difficulty Time Notes
3900 Longest Balanced Substring After One Swap 🟡 Medium 2m 17s We are given a binary string s containing only '0' and '1'. A subst…
3901 Good Subsequence Queries 🔴 Hard 2m 19s The solution does address the correct exercise and correctly identi…
3903 Smallest Stable Index I 🟢 Easy 2m 19s The problem asks us to find the smallest index i in an integer arra…
3904 Smallest Stable Index II 🟡 Medium 9m 17s The problem gives an integer array nums of length n and an integer …
3905 Multi Source Flood Fill 🟡 Medium 1m 12s The problem asks us to simulate a multi-source flood fill on an n x…
3906 Count Good Integers on a Grid Path 🔴 Hard 56s The solution does address the correct exercise and correctly identi…
3908 Valid Digit Number 🟢 Easy 1m 15s The problem is asking us to determine whether a given integer n is …
3909 Compare Sums of Bitonic Parts 🟡 Medium 1m 25s The problem gives us a bitonic array nums, meaning an array that fi…
3910 Count Connected Subgraphs with Even Node Sum 🔴 Hard 53s The solution does address the correct exercise and correctly identi…
3911 K-th Smallest Remaining Even Integer in Subarray Queries 🔴 Hard 1m 26s The problem provides a strictly increasing integer array nums and a…
3912 Valid Elements in an Array 🟢 Easy 55s The solution does address the correct exercise and correctly identi…
3913 Sort Vowels by Frequency 🟡 Medium 1m 6s The problem requires us to reorder the vowels in a given string s b…
3914 Minimum Operations to Make Array Non Decreasing 🟡 Medium 1m 13s We are given an array nums. In a single operation, we choose any co…
3915 Maximum Sum of Alternating Subsequence With Distance at Least K 🔴 Hard 53s The solution does address the correct exercise and correctly identi…
3917 Count Indices With Opposite Parity 🟢 Easy 1m 21s The problem gives us an integer array nums of length n. For every i…
3918 Sum of Primes Between Number and Its Reverse 🟡 Medium 1m 24s The problem gives us a single integer n. We first construct another…
3919 Minimum Cost to Move Between Indices 🟡 Medium 1m 29s We are given a strictly increasing array nums. Each position repres…
3920 Maximize Fixed Points After Deletions 🔴 Hard 1m 27s The problem asks us to maximize the number of fixed points in an ar…
3921 Score Validator 🟢 Easy 1m 21s This problem asks us to simulate a simple scoring system while proc…
3922 Minimum Flips to Make Binary String Coherent 🟡 Medium 1m 37s We are given a binary string s consisting only of '0' and '1'. A st…
3923 Minimum Generations to Target Point 🟡 Medium 1m 30s This problem defines a process that repeatedly creates new 3D point…
3924 Minimum Threshold Path With Limited Heavy Edges 🔴 Hard 1m 11s We are given an undirected weighted graph with n nodes and a list o…
3925 Concatenate Array With Reverse 🟢 Easy 1m 44s The problem asks us to construct a new array by concatenating an in…
3926 Count Valid Word Occurrences 🟡 Medium 1m 23s The problem asks us to count occurrences of specific words in a str…
3927 Minimize Array Sum Using Divisible Replacements 🟡 Medium 42s The problem gives an integer array nums and allows an operation tha…
3928 Minimum Cost to Buy Apples II 🔴 Hard 58s The problem asks us to determine the minimum cost to purchase apple…
3931 Check Adjacent Digit Differences 🟢 Easy 1m 5s The problem asks us to determine whether the absolute difference be…
3932 Count K-th Roots in a Range 🟡 Medium 1m 12s This problem asks us to count how many integers in a given range [l…
3933 Largest Local Values in a Matrix II 🟡 Medium 1m 24s The problem asks us to find local maximums in a 2D matrix according…
3934 Smallest Unique Subarray 🔴 Hard 1m 22s The problem asks us to find the smallest possible length of a conti…
3936 Minimum Swaps to Move Zeros to End 🟢 Easy 1m 14s The problem gives us an integer array nums containing values betwee…
3937 Minimum Operations to Make Array Modulo Alternating I 🟡 Medium 3m 6s The problem asks us to transform an array of integers, nums, into a…
3938 Maximum Path Intersection Sum in a Grid 🟡 Medium 2m 10s Here’s a fully detailed technical solution guide for LeetCode 3938,…
3939 Count Non Adjacent Subsets in a Rooted Tree 🔴 Hard 1m 40s We are given a rooted tree with n nodes. The tree is represented by…
3940 Limit Occurrences in Sorted Array 🟢 Easy 1m 32s This problem gives us a sorted integer array nums and an integer k.…
3941 Password Strength 🟡 Medium 1m 9s The problem requires calculating the strength of a password based o…
3942 Minimum Operations to Sort a Permutation 🟡 Medium 56s The problem gives an array nums that is guaranteed to be a permutat…
3943 Number of Pairs After Increment 🔴 Hard 1m 17s The problem gives two integer arrays nums1 and nums2 and a list of …
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LeetCode 3900 - Longest Balanced Substring After One Swap

We are given a binary string s containing only '0' and '1'. A substring is considered balanced when it contains exactly the same number of zeros and ones. Before choosing the substring, we are allowed to perform at most one swap between any two positions in the entire string.
leetcode Medium Jun 10, 2026
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LeetCode 3901 - Good Subsequence Queries

The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger.
leetcode Hard Jun 10, 2026
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LeetCode 3903 - Smallest Stable Index I

The problem asks us to find the smallest index i in an integer array nums such that the instability score at that index is less than or equal to a given integer k. The instability score is defined as the difference between the maximum of the prefix nums[0..
leetcode Easy array prefix-sum Jun 10, 2026
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LeetCode 3904 - Smallest Stable Index II

The problem gives an integer array nums of length n and an integer k. For every index i, we split the array into two overlapping parts: - The prefix nums[0..i] - The suffix nums[i..
leetcode Medium array prefix-sum Jun 10, 2026
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LeetCode 3905 - Multi Source Flood Fill

The problem asks us to simulate a multi-source flood fill on an n x m grid. Each element of the sources array represents a starting point with a specific color, and all other cells start uncolored, represented as 0.
leetcode Medium array breadth-first-search matrix Jun 10, 2026
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LeetCode 3906 - Count Good Integers on a Grid Path

The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger.
leetcode Hard dynamic-programming Jun 10, 2026
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LeetCode 3908 - Valid Digit Number

The problem is asking us to determine whether a given integer n is valid with respect to a digit x based on two conditions. First, n must contain at least one occurrence of the digit x. Second, n must not start with digit x.
leetcode Easy math Jun 10, 2026
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LeetCode 3909 - Compare Sums of Bitonic Parts

The problem gives us a bitonic array nums, meaning an array that first strictly increases to a single peak element and then strictly decreases. The task is to split this array into two overlapping parts: 1.
leetcode Medium array Jun 10, 2026
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LeetCode 3910 - Count Connected Subgraphs with Even Node Sum

The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger.
leetcode Hard array bit-manipulation depth-first-search breadth-first-search union-find graph-theory enumeration Jun 10, 2026
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LeetCode 3911 - K-th Smallest Remaining Even Integer in Subarray Queries

The problem provides a strictly increasing integer array nums and a list of queries, each consisting of [li, ri, ki]. For each query, we consider the subarray nums[li..ri] and remove all elements of this subarray from the infinite sequence of positive even integers.
leetcode Hard array binary-search Jun 10, 2026
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LeetCode 3912 - Valid Elements in an Array

The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger.
leetcode Easy array Jun 10, 2026
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LeetCode 3913 - Sort Vowels by Frequency

The problem requires us to reorder the vowels in a given string s based on their frequency, while keeping all consonants in their original positions. Specifically, the vowels must appear in non-increasing order of frequency.
leetcode Medium string sorting counting Jun 10, 2026
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LeetCode 3914 - Minimum Operations to Make Array Non Decreasing

We are given an array nums. In a single operation, we choose any contiguous subarray and increase every element in that subarray by the same positive integer value x. The cost of an operation is exactly the chosen value x.
leetcode Medium array greedy Jun 10, 2026
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LeetCode 3915 - Maximum Sum of Alternating Subsequence With Distance at Least K

The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger.
leetcode Hard array dynamic-programming segment-tree Jun 10, 2026
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LeetCode 3917 - Count Indices With Opposite Parity

The problem gives us an integer array nums of length n. For every index i, we must determine how many indices to its right contain a number with the opposite parity. Parity refers to whether a number is even or odd: - Even numbers have a remainder of 0 when divided by 2.
leetcode Easy array Jun 10, 2026
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LeetCode 3918 - Sum of Primes Between Number and Its Reverse

The problem gives us a single integer n. We first construct another integer r by reversing the digits of n. For example: - If n = 13, then r = 31 - If n = 10, then r = 1 - If n = 120, then r = 21 Once we have both numbers, we consider the inclusive range between them.
leetcode Medium math number-theory Jun 10, 2026
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LeetCode 3919 - Minimum Cost to Move Between Indices

We are given a strictly increasing array nums. Each position represents an index in the array, and we want to move between indices as cheaply as possible. For every index x, a special neighbor called closest(x) is defined.
leetcode Medium array greedy prefix-sum Jun 10, 2026
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LeetCode 3920 - Maximize Fixed Points After Deletions

The problem asks us to maximize the number of fixed points in an array after performing deletions. A fixed point is an index i such that nums[i] == i.
leetcode Hard array binary-search sorting Jun 10, 2026
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LeetCode 3921 - Score Validator

This problem asks us to simulate a simple scoring system while processing a sequence of event strings from left to right. We are given an array called events, where each element represents one event.
leetcode Easy array string simulation Jun 10, 2026
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LeetCode 3922 - Minimum Flips to Make Binary String Coherent

We are given a binary string s consisting only of '0' and '1'. A string is called coherent if it does not contain either of the following patterns as a subsequence: - "011" - "110" Recall that a subsequence does not need to occupy consecutive positions.
leetcode Medium string Jun 13, 2026
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LeetCode 3923 - Minimum Generations to Target Point

This problem defines a process that repeatedly creates new 3D points from existing points. We begin with the given list points, which forms generation 0.
leetcode Medium array hash-table simulation Jun 10, 2026
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LeetCode 3924 - Minimum Threshold Path With Limited Heavy Edges

We are given an undirected weighted graph with n nodes and a list of weighted edges. We must travel from source to target. The key concept in this problem is the definition of a threshold.
leetcode Hard binary-search breadth-first-search graph-theory Jun 13, 2026
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LeetCode 3925 - Concatenate Array With Reverse

The problem asks us to construct a new array by concatenating an input array with its reversed version. Given an integer array nums of length n, we must return a new array ans of length 2 n. The first n elements of ans are exactly the same as nums, preserving order.
leetcode Easy array simulation Jun 10, 2026
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LeetCode 3926 - Count Valid Word Occurrences

The problem asks us to count occurrences of specific words in a string that is formed by concatenating an array of smaller string "chunks".
leetcode Medium array hash-table string counting Jun 10, 2026
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LeetCode 3927 - Minimize Array Sum Using Divisible Replacements

The problem gives an integer array nums and allows an operation that can reduce values under a divisibility condition. Specifically, you may choose two indices a and b such that nums[a] % nums[b] == 0, and then replace nums[a] with nums[b].
leetcode Medium array hash-table math greedy number-theory Jun 10, 2026
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LeetCode 3928 - Minimum Cost to Buy Apples II

The problem asks us to determine the minimum cost to purchase apples starting from each shop, taking into account two types of costs: the local price of apples at each shop and the transportation costs along roads connecting the shops.
leetcode Hard array graph-theory heap-(priority-queue) shortest-path Jun 10, 2026
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LeetCode 3931 - Check Adjacent Digit Differences

The problem asks us to determine whether the absolute difference between every pair of adjacent digits in a given string s is at most 2. The input s is a string of digits, with a minimum length of 2 and a maximum of 100.
leetcode Easy string Jun 10, 2026
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LeetCode 3932 - Count K-th Roots in a Range

This problem asks us to count how many integers in a given range [l, r] are perfect kth powers, meaning each integer can be expressed as x^k for some integer x.
leetcode Medium math binary-search Jun 10, 2026
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LeetCode 3933 - Largest Local Values in a Matrix II

The problem asks us to find local maximums in a 2D matrix according to a specialized neighborhood rule. Each cell in the matrix has a value x.
leetcode Medium array matrix prefix-sum Jun 10, 2026
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LeetCode 3934 - Smallest Unique Subarray

The problem asks us to find the smallest possible length of a contiguous subarray such that there exists at least one subarray of that length that appears exactly once in the entire array.
leetcode Hard array hash-table binary-search rolling-hash suffix-array hash-function Jun 10, 2026
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LeetCode 3936 - Minimum Swaps to Move Zeros to End

The problem gives us an integer array nums containing values between 0 and 100. We may perform an operation where we choose any two distinct indices and swap their values. Our goal is to move all zeros to the end of the array while using the minimum possible number of swaps.
leetcode Easy Jun 10, 2026
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LeetCode 3937 - Minimum Operations to Make Array Modulo Alternating I

The problem asks us to transform an array of integers, nums, into a modulo alternating array with the minimum number of operations, where each operation is either incrementing or decrementing an element by 1.
leetcode Medium Jun 10, 2026
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LeetCode 3938 - Maximum Path Intersection Sum in a Grid

Here’s a fully detailed technical solution guide for LeetCode 3938, following your formatting and content requirements. The problem provides an m x n integer grid and two players with distinct movement constraints.
leetcode Medium Jun 10, 2026
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LeetCode 3939 - Count Non Adjacent Subsets in a Rooted Tree

We are given a rooted tree with n nodes. The tree is represented by the parent array, where parent[i] tells us the parent of node i. Node 0 is always the root because parent[0] = -1. Each node also has a value stored in nums[i].
leetcode Hard Jun 10, 2026
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LeetCode 3940 - Limit Occurrences in Sorted Array

This problem gives us a sorted integer array nums and an integer k. Our goal is to produce a result where every distinct value appears no more than k times. Because the array is already sorted in non-decreasing order, all occurrences of the same value appear consecutively.
leetcode Easy Jun 10, 2026
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LeetCode 3941 - Password Strength

The problem requires calculating the strength of a password based on its distinct characters. Each character type contributes differently to the strength: lowercase letters add 1 point, uppercase letters add 2 points, digits add 3 points, and special characters from "!
leetcode Medium Jun 10, 2026
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LeetCode 3942 - Minimum Operations to Sort a Permutation

The problem gives an array nums that is guaranteed to be a permutation of integers from 0 to n - 1. The goal is to transform this array into the sorted order [0, 1, 2, ..., n - 1] using only two allowed operations: a left rotation by one position and a full reversal of the array.
leetcode Medium Jun 10, 2026
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LeetCode 3943 - Number of Pairs After Increment

The problem gives two integer arrays nums1 and nums2 and a list of queries. Each query is either an increment operation on a subarray of nums2 or a pair-counting operation that asks for the number of pairs (j, k) such that nums1[j] + nums2[k] equals a target value tot.
leetcode Hard Jun 10, 2026