题目描述

Given an array nums, write a function to move all 0‘s to the end of it while maintaining the relative order of the non-zero elements.

Example:

1
2

Input: [0,1,0,3,12]
Output: [1,3,12,0,0]

Note:

1. You must do this in-place without making a copy of the array.
2. Minimize the total number of operations.

题目描述

Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middle value.

For example,

1
2

[2,3,4]`, the median is `3
[2,3]`, the median is `(2 + 3) / 2 = 2.5

Design a data structure that supports the following two operations:

• void addNum(int num) - Add a integer number from the data stream to the data structure.
• double findMedian() - Return the median of all elements so far.

Example:

1
2
3
4
5

addNum(1)
addNum(2)
findMedian() -> 1.5
addNum(3) 
findMedian() -> 2

题目描述

Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. Return the max sliding window.

Example:

1
2
3
4
5
6
7
8
9
10
11
12

Input: nums = [1,3,-1,-3,5,3,6,7], and k = 3
Output: [3,3,5,5,6,7] 
Explanation: 

Window position                Max
---------------               -----
[1  3  -1] -3  5  3  6  7       3
 1 [3  -1  -3] 5  3  6  7       3
 1  3 [-1  -3  5] 3  6  7       5
 1  3  -1 [-3  5  3] 6  7       5
 1  3  -1  -3 [5  3  6] 7       6
 1  3  -1  -3  5 [3  6  7]      7

题目描述

Given an integer, write a function to determine if it is a power of two.

Example 1:

1
2
3

Input: 1
Output: true 
Explanation: 20 = 1

Example 2:

1
2
3

Input: 16
Output: true
Explanation: 24 = 16

Example 3:

1
2

Input: 218
Output: false

题目描述

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.

Example 1:

1
2
3
4
5
6
7

Input: root = [3,1,4,null,2], k = 1
   3
  / \
 1   4
  \
   2
Output: 1

Example 2:

1
2
3
4
5
6
7
8
9

Input: root = [5,3,6,2,4,null,null,1], k = 3
       5
      / \
     3   6
    / \
   2   4
  /
 1
Output: 3

题目描述

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times.

Note: The algorithm should run in linear time and in O(1) space.

Example 1:

1
2

Input: [3,2,3]
Output: [3]

Example 2:

1
2

Input: [1,1,1,3,3,2,2,2]
Output: [1,2]

题目描述

Given a sorted integer array without duplicates, return the summary of its ranges.

Example 1:

1
2
3

Input:  [0,1,2,4,5,7]
Output: ["0->2","4->5","7"]
Explanation: 0,1,2 form a continuous range; 4,5 form a continuous range.

Example 2:

1
2
3

Input:  [0,2,3,4,6,8,9]
Output: ["0","2->4","6","8->9"]
Explanation: 2,3,4 form a continuous range; 8,9 form a continuous range.

题目描述

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.

The above elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Thanks Marcos for contributing this image!

Example:

1
2

Input: [0,1,0,2,1,0,1,3,2,1,2,1]
Output: 6

题目描述

Implement a basic calculator to evaluate a simple expression string.

The expression string contains only non-negative integers, +, -, *, / operators and empty spaces ``. The integer division should truncate toward zero.

Example 1:

1
2

Input: "3+2*2"
Output: 7

Example 2:

1
2

Input: " 3/2 "
Output: 1

Example 3:

1
2

Input: " 3+5 / 2 "
Output: 5

Note:

• You may assume that the given expression is always valid.
• Do not use the eval built-in library function.

题目描述

Invert a binary tree.

Example:

Input:

1
2
3
4
5

     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:

1
2
3
4
5

     4
   /   \
  7     2
 / \   / \
9   6 3   1