#UVa:10520-Determine it

照題目所述,製作出相同的遞迴式,並利用DP加速即可。

P.S. 在a19,1為499時,a1,19的值為4578345958,故得用long long來存取。

C++(0.149)

/*******************************************************/
/* UVa 10520 Determine it                              */
/* Author: LanyiKnight [at] knightzone.org             */
/* Version: 2014/09/25                                 */
/*******************************************************/
#include <iostream>
#include <cstdio>
#define A(x,y) (find_answer(dp, n, (x), (y)))
using namespace std;

long long find_answer(long long dp[][30], int n, int i, int j){
  if( dp[i][j] >= 0 ) return dp[i][j];

  if( i >= j ){
    long long ipart = 0, jpart = 0;
    if( i < n ){
      long long max_number = 0;
      for( int k = i+1 ; k <= n ; ++k ){
        long long temp = A(k, 1) + A(k, j);
        if( temp > max_number ) max_number = temp;
      }
      ipart = max_number;
    }

    if( j > 0 ){
      long long max_number = 0;
      for( int k = 1 ; k < j ; ++k ){
        long long temp = A(i, k) + A(n, k);
        if( temp > max_number ) max_number = temp;
      }
      jpart = max_number;
    }

    return dp[i][j] = ipart + jpart;
  } 
  else{
    long long max_number = 0;
    for( int k = i ; k < j ; ++k ){
      long long temp = A(i, k) + A(k+1, j);
      if( temp > max_number ) max_number = temp;
    }
    return dp[i][j] = max_number;

  }
}

int main(){
  int n;
  long long dp[30][30];
  while( scanf( "%d", &n ) != EOF ){
    for( int i = 0 ; i <= n ; ++i ){
      for( int j = 0 ; j <= n ; ++j ){
        dp[i][j] = -1;
      }
    }

    scanf("%lld", &dp[n][1]);

    printf( "%lld\n", A(1, n) );
  }
  return 0;
}

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