A string can be abbreviated by replacing any number of non-adjacent, non-empty substrings with their lengths. The lengths should not have leading zeros. For example, a string such as “substitution” could be abbreviated as (but not limited to): “s10n” (“s ubstitutio n”) “sub4u4” (“sub stit u tion”) “12” (“substitution”) “su3i1u2on” (“su bst i t u ti on”) “substitution” (no substrings replaced) The following are not valid abbreviations: ...
Given a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactly two or zero sub-node. If the node has two sub-nodes, then this node’s value is the smaller value among its two sub-nodes. More formally, the property root.val = min(root.left.val, root.right.val) always holds. Given such a binary tree, you need to output the second minimum value in the set made of all the nodes’ value in the whole tree. ...
The complement of an integer is the integer you get when you flip all the 0’s to 1’s and all the 1’s to 0’s in its binary representation. For example, The integer 5 is “101” in binary and its complement is “010” which is the integer 2. Given an integer n, return its complement. Example 1: Input: n = 5 Output: 2 Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10. Example 2: Input: n = 7 Output: 0 Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10. Example 3: Input: n = 10 Output: 5 Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10. Constraints: ...
Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters. Letters are case sensitive, for example, “Aa” is not considered a palindrome here. Example 1: Input: s = "abccccdd" Output: 7 Explanation: One longest palindrome that can be built is "dccaccd", whose length is 7. Example 2: Input: s = "a" Output: 1 Example 3: Input: s = "bb" Output: 2 Constraints: ...
Given a string s, return true if a permutation of the string could form a palindrome. Example 1: Input: s = "code" Output: false Example 2: Input: s = "aab" Output: true Example 3: Input: s = "carerac" Output: true Constraints: 1 <= s.length <= 5000 s consists of only lowercase English letters. Solution class Solution { public boolean canPermutePalindrome(String s) { int[] freq = new int[256]; for (char c: s.toCharArray()) { freq[c]++; } int count = 0; for (int f: freq) { count += f % 2; } return count <= 1; } }
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers. Given a string s, return true if it is a palindrome, or false otherwise. Example 1: Input: s = "A man, a plan, a canal: Panama" Output: true Explanation: "amanaplanacanalpanama" is a palindrome. Example 2: Input: s = "race a car" Output: false Explanation: "raceacar" is not a palindrome. Example 3: Input: s = " " Output: true Explanation: s is an empty string "" after removing non-alphanumeric characters. Since an empty string reads the same forward and backward, it is a palindrome. Constraints: ...
You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively. Merge nums1 and nums2 into a single array sorted in non-decreasing order. The final sorted array should not be returned by the function, but instead be stored inside the array nums1. To accommodate this, nums1 has a length of m + n, where the first m elements denote the elements that should be merged, and the last n elements are set to 0 and should be ignored. nums2 has a length of n. ...
Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Since it is impossible to change the length of the array in some languages, you must instead have the result be placed in the first part of the array nums. More formally, if there are k elements after removing the duplicates, then the first k elements of nums should hold the final result. It does not matter what you leave beyond the first k elements. ...
Given two integer arrays of equal length target and arr. In one step, you can select any non-empty sub-array of arr and reverse it. You are allowed to make any number of steps. Return True if you can make arr equal to target, or False otherwise. Example 1: Input: target = [1,2,3,4], arr = [2,4,1,3] Output: true Explanation: You can follow the next steps to convert arr to target: 1- Reverse sub-array [2,4,1], arr becomes [1,4,2,3] 2- Reverse sub-array [4,2], arr becomes [1,2,4,3] 3- Reverse sub-array [4,3], arr becomes [1,2,3,4] There are multiple ways to convert arr to target, this is not the only way to do so. Example 2: Input: target = [7], arr = [7] Output: true Explanation: arr is equal to target without any reverses. Example 3: Input: target = [1,12], arr = [12,1] Output: true Example 4: Input: target = [3,7,9], arr = [3,7,11] Output: false Explanation: arr doesn't have value 9 and it can never be converted to target. Example 5: Input: target = [1,1,1,1,1], arr = [1,1,1,1,1] Output: true Constraints: ...
Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1. You must write an algorithm with O(log n) runtime complexity. Example 1: Input: nums = [-1,0,3,5,9,12], target = 9 Output: 4 Explanation: 9 exists in nums and its index is 4 Example 2: Input: nums = [-1,0,3,5,9,12], target = 2 Output: -1 Explanation: 2 does not exist in nums so return -1 Constraints: ...