Coding for Dreams

题目：有两个长为n的非递减数组A和B，把B接在A的后面变成长为2n的数组C。设计算法求C的中位数（第n小数）。思路：O(n)的算法很容易找到，关键是用二分的思想设计logn算法。这题关键是用好a和b数组中脚标和为定值的元素的大小关系。            直观想法是：如果中位数在数组a中，那么若a[m] b [n-m-1],此时比a[m]小的数至少有n个，a[m]不可能为第n小数，偏大更

Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.Note: You may assume k is always valid, 1 ≤ k ≤ BST's total elements.Follow up:What if the BST is modifi

Follow up for "Find Minimum in Rotated Sorted Array":What if duplicates are allowed?Would this affect the run-time complexity? How and why?Suppose a sorted array is rotated at some pivot unknown to yo

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j is

Given an unsorted integer array, find the first missing positive integer.For example,Given [1,2,0] return 3,and [3,4,-1,1] return 2.Your algorithm should run in O(n) time and uses constant space.思路分析：

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 inde

A peak element is an element that is greater than its neighbors.Given an input array where num[i] ≠ num[i+1], find a peak element and return its index.The array may contain multiple peaks, in that cas

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 inde

There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).思路分析：这题容易想到O(m+n)的解法，就是先Merge两个数组，然后返

LeetCode Pow(x, n) Implement pow(x, n).s

首先要区分#include 中的qsort与C++ STL algorithm中的sort，后者只有三个参数且比较函数写法较简单些 类似于POJ 1065,差异有二，其一是排序方式下降，其二是要求下降且不相等但是用常规的贪心会超时,用二分优化后不超时，注意对l递增排，对w递减排// 类似于POJ 1065,差异有二，其一是排序方式下降，其二是要求下降且不相等// 上面这种解法会超时,用二分优化

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).Find the minimum element.You may assume no duplicate exists in the array.思路分析