Python 刷Leetcode题库，顺带学英语单词（11）

First Missing Positive

Given an unsorted integer array, find the smallest missing positive integer.    [#41]

Example:
Input: [1,2,0]
Output: 3
Input: [3,4,-1,1]
Output: 2
Input: [7,8,9,11,12]
Output: 1

Note:

Your algorithm should run in O(n) time and uses constant extra space.

Trapping Rain Water

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