[HRBUST1472] Coin (DP, Count)

Title Link: http://acm-software.hrbust.edu.cn/problem.php?id=1472

Test instructions: Give n a coin, the face value is random. Ask the number of categories that happen to be in M-dollar (remove duplicates).

DP (I,J,K) denotes i-coins, J-elements, and the maximum number of classes of K.

At first, the mentally retarded memory Dfs burst T is more than just a recursive or a T.

The result is to consider adding some pruning to the memory Dfs first, or T.

The recursion to do some processing, found that because the current maximum enumeration, the largest L if it is j+2, even if it is only one, is greater than j+1. To see here, is forward to recursion, that is to say, the minimum par value of the topic is 1, in the recursive time just maintain in J is not satisfied, need to j+1.

1#include <bits/stdc++.h>2 using namespacestd;3typedefLong LongLL;4 ConstLL mod =2000000007;5 Const intMAXN = -;6 LL DP[MAXN][MAXN][MAXN];7 intN, M;8 9LL DFS (intNintMintpre) {Ten     if(Dp[n][m][pre]! =-1)returnDp[n][m][pre]; One     //if (pre > M) return dp[n][m][pre] = 0; A     if(n = =0) { -         if(M = =0)returnDp[n][m][pre] =1; -         returnDp[n][m][pre] =0; the     } -Dp[n][m][pre] =0; -      for(inti = Pre; I <= m; i++) { -         if(M-i <0) Break; +Dp[n][m][pre] = (Dp[n][m][pre] + DFS (n-1, M-i, i))%MoD; -     } +     returnDp[n][m][pre]; A } at  - intMain () { -     //freopen ("in", "R", stdin); -     intT; -scanf"%d", &T); -Memset (DP,0,sizeof(DP)); indp[1][1][1] =1; -      for(inti =1; I <= $; i++) { to          for(intj =1; J <= $; J + +) { +              for(intK =1; K <= $; k++) { -                 if(Dp[i][j][k] = =0)Continue; the                  for(intL = k; J + L <= $; l++) { *                     if(L > J +1) Break; $dp[i+1][j+l][l] = (dp[i+1][J+L][L] + dp[i][j][k])%MoD;Panax Notoginseng                 } -             } the         } +     } A      while(t--) { thescanf"%d%d",&n,&m); +LL ret =0; -          for(inti =1; I <= m; i++) { $RET = (ret + dp[n][m][i])%MoD; $         } -printf"%lld\n", ret); -     } the     return 0; -}

[HRBUST1472] Coin (DP, Count)