Leetcode

1099. Two Sum Less Than K Given an array nums of integers and integer k, return the maximum sum such that there exists i < j with nums[i] + nums[j] = sum and sum < k. If no i, j exist satisfying this equation, return -1. Example 1: Input: nums = [34,23,1,24,75,33,54,8], k = 60 Output: 58 Explanation: We can use 34 and 24 to sum 58 which is less than 60. Example 2: Input: nums = [10,20,30], k = 15 Output: -1 Explanation: In this case it is not possible to get a pair sum less that 15. Constraints: ...

19. Remove Nth Node From End of List Given the head of a linked list, remove the nth node from the end of the list and return its head. Example 1: Input: head = [1,2,3,4,5], n = 2 Output: [1,2,3,5] Example 2: Input: head = [1], n = 1 Output: [] Example 3: Input: head = [1,2], n = 1 Output: [1] Constraints: The number of nodes in the list is sz. 1 <= sz <= 30 0 <= Node.val <= 100 1 <= n <= sz Solution /** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */ class Solution { public ListNode removeNthFromEnd(ListNode head, int n) { ListNode dummy = new ListNode(0); dummy.next= head; ListNode walker = dummy; ListNode runner = dummy; for (int i = 0; i < n + 1; i++) { runner = runner.next; } while (runner != null) { walker = walker.next; runner = runner.next; } walker.next = walker.next.next; return dummy.next; } }

2. Add Two Numbers You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list. You may assume the two numbers do not contain any leading zero, except the number 0 itself. Example 1: Input: l1 = [2,4,3], l2 = [5,6,4] Output: [7,0,8] Explanation: 342 + 465 = 807. ...

523. Continuous Subarray Sum Given an integer array nums and an integer k, return true if nums has a continuous subarray of size at least two whose elements sum up to a multiple of k, or false otherwise. An integer x is a multiple of k if there exists an integer n such that x = n * k. 0 is always a multiple of k. Example 1: Input: nums = [23,2,4,6,7], k = 6 Output: true Explanation: [2, 4] is a continuous subarray of size 2 whose elements sum up to 6. Example 2: Input: nums = [23,2,6,4,7], k = 6 Output: true Explanation: [23, 2, 6, 4, 7] is an continuous subarray of size 5 whose elements sum up to 42. 42 is a multiple of 6 because 42 = 7 * 6 and 7 is an integer. Example 3: Input: nums = [23,2,6,4,7], k = 13 Output: false Constraints: ...

67. Add Binary Given two binary strings a and b, return their sum as a binary string. Example 1: Input: a = "11", b = "1" Output: "100" Example 2: Input: a = "1010", b = "1011" Output: "10101" Constraints: 1 <= a.length, b.length <= 104 a and b consist only of ‘0’ or ‘1’ characters. Each string does not contain leading zeros except for the zero itself. Solution class Solution { public String addBinary(String a, String b) { int i = a.length() - 1; int j = b.length() - 1; int carry = 0; StringBuilder sb = new StringBuilder(); while (i >= 0 || j >= 0) { int c1 = (i >= 0) ? a.charAt(i) - '0': 0; int c2 = (j >= 0) ? b.charAt(j) - '0': 0; int c3 = c1 + c2 + carry; if (carry > 0) { carry = 0; } if (c3 == 3) { carry = 1; sb.insert(0, '1'); } else if (c3 == 2) { carry = 1; sb.insert(0, '0'); } else if (c3 == 1) { sb.insert(0, '1'); } else { sb.insert(0, '0'); } i--; j--; } if (carry > 0) { sb.insert(0, '1'); } return sb.toString(); } public String addBinary2(String a, String b) { Integer i1 = Integer.parseInt(a, 2); Integer i2 = Integer.parseInt(b, 2); return Integer.toBinaryString(i1 + i2); } }

974. Subarray Sums Divisible by K Given an array nums of integers, return the number of (contiguous, non-empty) subarrays that have a sum divisible by k. Example 1: Input: nums = [4,5,0,-2,-3,1], k = 5 Output: 7 Explanation: There are 7 subarrays with a sum divisible by k = 5: [4, 5, 0, -2, -3, 1], [5], [5, 0], [5, 0, -2, -3], [0], [0, -2, -3], [-2, -3] Note: ...

1897. Redistribute Characters to Make All Strings Equal You are given an array of strings words (0-indexed). In one operation, pick two distinct indices i and j, where words[i] is a non-empty string, and move any character from words[i] to any position in words[j]. Return true if you can make every string in words equal using any number of operations, and false otherwise. Example 1: Input: words = ["abc","aabc","bc"] Output: true Explanation: Move the first 'a' in words[1] to the front of words[2], to make words[1] = "abc" and words[2] = "abc". All the strings are now equal to "abc", so return true. Example 2: Input: words = ["ab","a"] Output: false Explanation: It is impossible to make all the strings equal using the operation. Constraints: ...

1898. Maximum Number of Removable Characters You are given two strings s and p where p is a subsequence of s. You are also given a distinct 0-indexed integer array removable containing a subset of indices of s (s is also 0-indexed). You want to choose an integer k (0 <= k <= removable.length) such that, after removing k characters from s using the first k indices in removable, p is still a subsequence of s. More formally, you will mark the character at s[removable[i]] for each 0 <= i < k, then remove all marked characters and check if p is still a subsequence. ...

1899. Merge Triplets to Form Target Triplet A triplet is an array of three integers. You are given a 2D integer array triplets, where triplets[i] = [ai, bi, ci] describes the ith triplet. You are also given an integer array target = [x, y, z] that describes the triplet you want to obtain. To obtain target, you may apply the following operation on triplets any number of times (possibly zero): ...

31. Next Permutation Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers. If such an arrangement is not possible, it must rearrange it as the lowest possible order (i.e., sorted in ascending order). The replacement must be in place and use only constant extra memory. Example 1: Input: nums = [1,2,3] Output: [1,3,2] Example 2: Input: nums = [3,2,1] Output: [1,2,3] Example 3: Input: nums = [1,1,5] Output: [1,5,1] Example 4: Input: nums = [1] Output: [1] Constraints: ...