Algo: Two Sum

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类似的题目可以用HashTable的思想解决. 1.Two Sum Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice. ht…

308. Range Sum Query 2D - Mutable

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307. Range Sum Query - Mutable

题目: Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. The update(i, val) function modifies nums by updating the element at index i to val. Example: Given nums = [1, 3, 5] sumRange(0, 2) -> 9 update(…

LeetCode解题报告—— Sum Root to Leaf Numbers & Surrounded Regions & Single Number II

1. Sum Root to Leaf Numbers Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3 which represents the number 123. Find the total sum of all root-to-leaf num…

LeetCode - Two Sum

Two Sum 題目連結官網題目說明: 解法: 從給定的一組值內找出第一組兩數相加剛好等於給定的目標值,暴力解很簡單(只會這樣= =),兩個迴圈,只要找到相加的值就跳出. /// <summary> /// 暴力解O(n) /// </summary> /// <param name="nums"></param> /// <param name="target"></param> /// &…

Leetcode 笔记 113 - Path Sum II

题目链接:Path Sum II | LeetCode OJ 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 and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2],…

Leetcode 笔记 112 - Path Sum

题目链接:Path Sum | LeetCode OJ 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 and sum = 22, 5 / \ 4 8 / / \ 11…