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전체 글137

LeetCode. Min Stack Problem: Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) -- Push element x onto stack. pop() -- Removes the element on top of the stack. top() -- Get the top element. getMin() -- Retrieve the minimum element in the stack. Example 1: -Summary- Use tuple to save the minimum value and the current value of the stack. class MinStack: def __ini.. 2020. 6. 26.
LeetCode. Shuffle an Array Problem: Shuffle a set of numbers without duplicates. Example: // Init an array with set 1, 2, and 3. int[] nums = {1,2,3}; Solution solution = new Solution(nums); // Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned. solution.shuffle(); // Resets the array back to its original configuration [1,2,3]. solution.reset(); // Returns the ra.. 2020. 6. 24.
LeetCode. Count Complete Tree Nodes Problem: Given a complete binary tree, count the number of nodes. Note: Definition of a complete binary tree from Wikipedia: In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h. Example: -Summary- Solve by recursion 1. if the root exists.. 2020. 6. 24.
LeetCode.Single Number II Problem: Given a non-empty array of integers, every element appears three times except for one, which appears exactly once. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? Example 1: Input: [2,2,3,2] Output: 3 Example 2: Input: [0,1,0,1,0,1,99] Output: 99 -Summary- Solved by using dictionary. 1. for each numbe.. 2020. 6. 23.
LeetCode. Reverse Bits Problem: Reverse bits of a given 32 bits unsigned integer. Example 1: Input: 00000010100101000001111010011100 Output: 00111001011110000010100101000000 Explanation: The input binary string 00000010100101000001111010011100 represents the unsigned integer 43261596, so return 964176192 which its binary representation is 00111001011110000010100101000000. Example 2: Input: 1111111111111111111111111111.. 2020. 6. 22.
LeetCode 91. Decode Ways Problem: A message containing letters from A-Z is being encoded to numbers using the following mapping:'A' -> 1 'B' -> 2 ... 'Z' -> 26 Given a non-empty string containing only digits, determine the total number of ways to decode it. Example 1: Input: "12" Output: 2 Explanation: It could be decoded as "AB" (1 2) or "L" (12). Example 2: Input: "226" Output: 3 Explanation: It could be decoded as "B.. 2020. 6. 21.