链接：

https://codeforces.com/contest/1176/problem/C

题意：

You are given an array a consisting of n integers. Each ai is one of the six following numbers: 4,8,15,16,23,42.

Your task is to remove the minimum number of elements to make this array good.

An array of length k is called good if k is divisible by 6 and it is possible to split it into k6 subsequences 4,8,15,16,23,42.

Examples of good arrays:

[4,8,15,16,23,42] (the whole array is a required sequence); [4,8,4,15,16,8,23,15,16,42,23,42] (the first sequence is formed from first, second, fourth, fifth, seventh and tenth elements and the second one is formed from remaining elements); [] (the empty array is good). Examples of bad arrays:

[4,8,15,16,42,23] (the order of elements should be exactly 4,8,15,16,23,42); [4,8,15,16,23,42,4] (the length of the array is not divisible by 6); [4,8,15,16,23,42,4,8,15,16,23,23] (the first sequence can be formed from first six elements but the remaining array cannot form the required sequence).

思路：

刚开始题目看错。。以为任意顺序的子序列。 map将值映射到1-6，然后每次遇到2-5中的x，从x-1的个数中移一个到x，最后看能移几个到6.

代码：

1#include <bits/stdc++.h>
2
3using namespace std;
4
5typedef long long LL;
6const int MAXN = 3e5 + 10;
7const int MOD = 1e9 + 7;
8int n, m, k, t;
9
10map<int, int> mp;
11
12int main()
13{
14    cin >> n;
15    mp[4] = 1;
16    mp[8] = 2;
17    mp[15] = 3;
18    mp[16] = 4;
19    mp[23] = 5;
20    mp[42] = 6;
21    int vis[10] = {0};
22    int res = 0, temp = 0;
23    int last = 1;
24    int flag = 0;
25    for (int i = 1;i <= n;i++)
26    {
27        int v;
28        cin >> v;
29        if (mp[v] == 1)
30            vis[mp[v]]++;
31        else if (vis[mp[v]-1]>0)
32        {
33            vis[mp[v]-1]--;
34            vis[mp[v]]++;
35        }
36    }
37    cout << n-6*vis[6] << endl;
38
39    return 0;
40}