ural 1431. Diplomas

  1 /**
  2 Create By yzx - stupidboy
  3 */
  4 #include <cstdio>
  5 #include <cstring>
  6 #include <cstdlib>
  7 #include <cmath>
  8 #include <deque>
  9 #include <vector>
 10 #include <queue>
 11 #include <iostream>
 12 #include <algorithm>
 13 #include <map>
 14 #include <set>
 15 #include <ctime>
 16 #include <iomanip>
 17 using namespace std;
 18 typedef long long LL;
 19 typedef double DB;
 20 #define For(i, s, t) for(int i = (s); i <= (t); i++)
 21 #define Ford(i, s, t) for(int i = (s); i >= (t); i--)
 22 #define Rep(i, t) for(int i = (0); i < (t); i++)
 23 #define Repn(i, t) for(int i = ((t)-1); i >= (0); i--)
 24 #define rep(i, x, t) for(int i = (x); i < (t); i++)
 25 #define MIT (2147483647)
 26 #define INF (1000000001)
 27 #define MLL (1000000000000000001LL)
 28 #define sz(x) ((int) (x).size())
 29 #define clr(x, y) memset(x, y, sizeof(x))
 30 #define puf push_front
 31 #define pub push_back
 32 #define pof pop_front
 33 #define pob pop_back
 34 #define ft first
 35 #define sd second
 36 #define mk make_pair
 37 inline void SetIO(string Name)
 38 {
 39     string Input = Name+".in",
 40     Output = Name+".out";
 41     freopen(Input.c_str(), "r", stdin),
 42     freopen(Output.c_str(), "w", stdout);
 43 }
 44 
 45 
 46 inline int Getint()
 47 {
 48     int Ret = 0;
 49     char Ch = ‘ ‘;
 50     bool Flag = 0;
 51     while(!(Ch >= ‘0‘ && Ch <= ‘9‘))
 52     {
 53         if(Ch == ‘-‘) Flag ^= 1;
 54         Ch = getchar();
 55     }
 56     while(Ch >= ‘0‘ && Ch <= ‘9‘)
 57     {
 58         Ret = Ret * 10 + Ch - ‘0‘;
 59         Ch = getchar();
 60     }
 61     return Flag ? -Ret : Ret;
 62 }
 63 
 64 const int N = 19;
 65 int n, Arr[N];
 66 int Dp[N][1 << N];
 67 
 68 inline void Input()
 69 {
 70     scanf("%d", &n);
 71     For(i, 1, n) scanf("%d", &Arr[i]);
 72 }
 73 
 74 inline int Val(int x)
 75 {
 76     return 1 << (x - 1);
 77 }
 78 
 79 inline void Search(int x, int State, int Cnt)
 80 {
 81     if(Dp[x - 1][State] <= Cnt) return;
 82     Dp[x - 1][State] = Cnt;
 83     if(x > n) return ;
 84     if(State & Val(x))
 85     {
 86         Search(x + 1, State, Cnt);
 87         return;
 88     }
 89     Search(x + 1, State | Val(x), Cnt + 1);
 90     For(i, x + 1, n)
 91         if(!(State & Val(i)) && abs(Arr[i] - Arr[x]) == 1)
 92             Search(x + 1, State | Val(x) | Val(i), Cnt + 1);
 93 }
 94 
 95 inline void Solve()
 96 {
 97     clr(Dp, 63);
 98     Search(1, 0, 0);
 99     cout << Dp[n][(1 << n) - 1] << endl;
100 }
101 
102 int main()
103 {
104     #ifndef ONLINE_JUDGE
105     SetIO("A");
106     #endif
107     Input();
108     Solve();
109     return 0;
110 }