CF1079C Playing Piano

思路：

dp。

实现：

 #include <bits/stdc++.h>
 using namespace std;
 int a[], dp[][];
 int main()
 {
     int n;
     while (cin >> n)
     {
         for (int i = ; i <= n; i++) cin >> a[i];
         memset(dp, , sizeof dp);
         for (int i = ; i <= ; i++) dp[][i] = ;
         for (int i = ; i <= n; i++)
         {
             for (int j = ; j <= ; j++)
             {
                 if (a[i] > a[i - ])
                 {
                     for (int k = ; k < j; k++)
                     {
                         if (dp[i - ][k]) dp[i][j] = k;
                     }
                 }
                 else if (a[i] < a[i - ])
                 {
                     for (int k = j + ; k <= ; k++)
                     {
                         if (dp[i - ][k]) dp[i][j] = k;
                     }
                 }
                 else
                 {
                     for (int k = ; k <= ; k++)
                     {
                         if (k != j && dp[i - ][k]) dp[i][j] = k;
                     }
                 }
             }
         }
         bool flg = false;
         int i = ;
         for ( ; i <= ; i++)
         {
             if (dp[n][i]) { flg = true; break; }
         }
         if (!flg) cout << "-1" << endl;
         else
         {
             vector<int> v;
             v.push_back(i);
             int now = n;
             while (now >= )
             {
                 v.push_back(dp[now][i]);
                 i = dp[now][i];
                 now--;
             }
             for (int i = v.size() - ; i >= ; i--) cout << v[i] << " ";
             cout << endl;
         }
     }
     return ;
 }