C++17在业务代码中最好用的十个特性

自从步入现代C++时代开始，C++语言标准形成了三年一个版本的惯例：C++11标志着现代C++的开端，C++14在11的基础上查缺补漏，并未加入许多新特性，而C++17作为C++11后的第一个大版本，标志着现代C++逐渐走向成熟。WXG编译器升级到gcc7.5已有一段时间，笔者所在项目组也已经将全部代码升级到C++17。在使用了c++17一年多之后，笔者总结了C++17在业务代码中最好用的十个特性。

Tree traversal algorithms: pre_order, in_order, post_order

SweepLine algorithm for finding all intersections

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Implement atoi which converts a string to an integer.

Given a list of daily temperatures T, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.

Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.

Given a 32-bit signed integer, reverse digits of an integer.

Given a string, your task is to count how many palindromic substrings in this string.

Given a char array representing tasks CPU need to do. It contains capital letters A to Z where different letters represent different tasks. Tasks could be done without original order. Each task could be done in one interval. For each interval, CPU could finish one task or just be idle.

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not.

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

Given an integer array, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order, too.

Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

You are given a list of non-negative integers, a1, a2, …, an, and a target, S. Now you have 2 symbols + and -. For each integer, you should choose one from + and - as its new symbol.

Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.

Given a string s and a non-empty string p, find all the start indices of p’s anagrams in s.

You are given a binary tree in which each node contains an integer value.

Given a non-empty array containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this person who have a height greater than or equal to h. Write an algorithm to reconstruct the queue.

There are two sorted arrays nums1 and nums2 of size m and n respectively.

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

Given a string, find the length of the longest substring without repeating characters.

Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator.

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.

Given a linked list, swap every two adjacent nodes and return its head.

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Given a string containing just the characters '(', ')', '{', '}', '['and ']', determine if the input string is valid.

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Given a linked list, remove the n-th node from the end of list and return its head.

Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.

Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

Given an array nums of n integers, are there elements a, b, c in numssuch that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Write a function to find the longest common prefix string amongst an array of strings.

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Given an integer n, your task is to count how many strings of length n can be formed under the following rules:

In a gold mine grid of size m * n, each cell in this mine has an integer representing the amount of gold in that cell, 0 if it is empty.

Given an integer array arr and an integer difference, return the length of the longest subsequence in arr which is an arithmetic sequence such that the difference between adjacent elements in the subsequence equals difference.

There are some chips, and the i-th chip is at position chips[i].

In an n*n grid, there is a snake that spans 2 cells and starts moving from the top left corner at (0, 0) and (0, 1). The grid has empty cells represented by zeros and blocked cells represented by ones. The snake wants to reach the lower right corner at (n-1, n-2) and (n-1, n-1).

Given a string s, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them causing the left and the right side of the deleted substring to concatenate together.

You are given two strings s and t of the same length. You want to change s to t. Changing the i-th character of s to i-th character of t costs |s[i] - t[i]| that is, the absolute difference between the ASCII values of the characters.

Given an array of integers arr, write a function that returns true if and only if the number of occurrences of each value in the array is unique.

There are n items each belonging to zero or one of m groups where group[i] is the group that the i-th item belongs to and it’s equal to -1 if the i-th item belongs to no group. The items and the groups are zero indexed. A group can have no item belonging to it.

You are given a string s, and an array of pairs of indices in the string pairs where pairs[i] = [a, b] indicates 2 indices(0-indexed) of the string.

Write a program to find the n-th ugly number.

Given an array of distinct integers arr, find all pairs of elements with the minimum absolute difference of any two elements.

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

There are n servers numbered from 0 to n-1 connected by undirected server-to-server connections forming a network where connections[i] = [a, b] represents a connection between servers a and b. Any server can reach any other server directly or indirectly through the network.

Given an integer array arr and an integer k, modify the array by repeating it k times.

You are given a string s that consists of lower case English letters and brackets.

With respect to a given puzzlewordvalid

Given a string s, we make queries on substrings of s.

A dieter consumes calories[i] calories on the i-th day. For every consecutive sequence of k days, they look at T, the total calories consumed during that sequence of k days:

Return the number of permutations of 1 to n so that prime numbers are at prime indices (1-indexed.)

Given n non-negative integers a1, a2, …, an , where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.

Given an input string (s) and a pattern (p), implement regular expression matching with support for '.' and '*'.

Given an array of integers, return indices of the two numbers such that they add up to a specific target.