代码面试C++/STL Cheat Sheet

在以前的面试指南中，写代码不限定编程语言，主要考察算法。近几年机器学习火了之后，作为面试官，面试科班出身的面试者我会要求对方使用C或C++而非Python。原因很简单，现在许多科班出身的同学基本功不扎实，恨不能大一上来就搞深度学习，对计算机科学没有大局观和底层的认识，往往不能很好地胜任日常的工作。而C/C++作为科班的必修课，可以作为一个简单的分类器判断对方的功底。

吐槽完毕，LeetCode是大家常用来刷题的网站，但对于工作中不把C/C++作为开发语言的工程师来说有些语法太久不用就忘了，更不提STL中的一些特殊数据结构的方法，这里简单总结一下，便于快速捡起来。

#include <iostream>
#include <climits>
#include <vector>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
#include <deque>

using namespace std;

int main()
{
    // Constants
    cout<<"INT_MAX: "<<INT_MAX<<endl;
    cout<<"INT_MIN: "<<INT_MIN<<endl;

    // Vector
    vector<int> v(3, 0);  // Init a 1 * 3 vector with value 0
    v.push_back(0);
    v.pop_back();
    cout<<"Final vector size: "<<v.size()<<endl;

    vector<vector<int>> v2d(3, vector<int>(5, 0)); // Init a 3 * 5 2d vector with value 0
    cout<<"2d vector size: "<<v2d.size()<<" * "<<v2d[0].size()<<endl;

    // Map & unordered_map
    unordered_map<int, int> m;
    m[0] = 1;
    m.erase(0);
    cout<<"Final map size: "<<m.size()<<endl;

    // Set & unordered_set
    unordered_set<int> s;
    s.insert(0);
    s.erase(0);
    cout<<"Final set size: "<<s.size()<<endl;

    // Stack
    stack<int> stk;
    stk.push(0);
    int stackTop = stk.top();
    stk.pop();
    cout<<"Final stack size: "<<stk.size()<<endl;

    // Queue
    queue<int> q;
    q.push(0);
    int qFront = q.front();
    q.pop();
    cout<<"Final queue size: "<<q.size()<<endl;

    // Deque
    deque<int> deq;
    deq.push_front(0);
    deq.push_back(1);
    int deqFront = deq.front();
    int deqBack = deq.back();
    cout<<"Deque: "<<deqFront<<" "<<deqBack<<endl;
    deq.pop_front();
    deq.pop_back();
    cout<<"Final deque size: "<<deq.size()<<endl;

    // Priority Queue
    priority_queue<int> pq; // max heap
    pq.push(0); pq.push(1);
    int pqTop = pq.top();
    cout<<"Priority queue top: "<<pqTop<<endl;
    pq.pop();
    cout<<"Final priority queue size: "<<pq.size()<<endl;
}

运行结果：

INT_MAX: 2147483647
INT_MIN: -2147483648
Final vector size: 3
2d vector size: 3 * 5
Final map size: 0
Final set size: 0
Final stack size: 0
Final queue size: 0
Deque: 0 1
Final deque size: 0
Priority queue top: 1
Final priority queue size: 1