随笔分类 - LeetCode
摘要：Given a binary tree, find the maximum path sum.The path may start and end at any node in the tree.For example:Given the below binary tree, 1 / \ 2 3Return6./** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode...
阅读全文
摘要：Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.思考：DFS。/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) ...
阅读全文
摘要：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3But the following is not: 1 / \ 2 2 \ \ 3 3Note:Bonus points if you could solve it both recursively and iterati...
阅读全文
摘要：Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.思考：考虑[1,2]这种情况，返回树最低高度为2。所以分两种情况，有一棵子树不在时，返回另一棵子树树高+1，否则返回矮子树高+1./** * Definition for binary tree * struct TreeNode { * int val; * Tre...
阅读全文
摘要：Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.For example:Given the below binary tree andsum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1return[ [5,4,11,2]...
阅读全文
摘要：Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value.思考：DFS./** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right...
阅读全文
摘要：Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary tree andsum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ ...
阅读全文
摘要：Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [2], [3,4], [6,5,7], [4,1,8,3]]The minimum path sum from top to bottom is11(i.e.,2+3+5+1= 11).Note:Bonus point if you are a...
阅读全文
摘要：Given a linked list and a valuex, partition it such that all nodes less thanxcome before nodes greater than or equal tox.You should preserve the original relative order of the nodes in each of the two partitions.For example,Given1->4->3->2->5->2andx= 3,return1->2->2->4->3-
阅读全文
摘要：The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...1is read off as"one 1"or11.11is read off as"two 1s"or21.21is read off as"one 2, thenone 1"or1211.Given an integern, generate thenthsequence.Note: The sequence of inte
阅读全文
摘要：Write a program to solve a Sudoku puzzle by filling the empty cells.Empty cells are indicated by the character '.'.You may assume that there will be only one unique solution.A sudoku puzzle......and its solution numbers marked in red.思考：参考这里。class Solution {public: // 返回第一个空白的位置，如果没找到就返回 (-1
阅读全文
摘要：Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character '.'.A partially filled sudoku which is valid.思考：参考这里。class Solution {public: bool isValidSudoku(vector > &board) { vecto
阅读全文
摘要：Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.You may assume no duplicates in the array.Here are few examples.[1,3,5,6], 5 → 2 [1,3,5,6], 2 → 1 [1,3,5,6], 7 → 4[1,3,5,6], 0 → 0思考：二分搜索。class So
阅读全文
摘要：Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another expression.Some examples: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "
阅读全文
摘要：Suppose a sorted array is rotated at some pivot unknown to you beforehand.(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).You are given a target value to search. If found in the array return its index, otherwise return -1.You may assume no duplicate exists in the array.思考：二分搜索。class Solution {publi
阅读全文
摘要：Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.For "(()", the longest valid parentheses substring is "()", which has length = 2.Another example is ")()())", where the lo
阅读全文
摘要：Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).The replacement must be in-place, do not allocate extra memory.He
阅读全文
摘要：You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatena...
阅读全文
摘要：Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.You may not alter the values in the nodes, only nodes itself may be changed.Only constant memory is all
阅读全文
摘要：Divide two integers without using multiplication, division and mod operator.思考：位运算。AC的时候真的想说一句“尼玛。。“，用unsigned int 超时，莫名其妙，折腾到半夜，百度一下改为long long过了。。我也不明白到底怎么回事，毕竟不是CS出身，哎。。太晚了，明天再看。VC不支持long long，珍爱生命，远离VC。class Solution {public: int divide(int dividend, int divisor) { // IMPORTANT: Please...
阅读全文
浙公网安备 33010602011771号