UVa : 11420 (Chest of Drawers)



// link: http://uva.onlinejudge.org/external/114/11420.html
// Runtime: 0.364s
// Tag: Recur, dp


//============================================================================
// Name        : Test.cpp
// Author      : Shahab
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

// @BEGIN_OF_SOURCE_CODE

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cctype>
#include <stack>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <sstream>
#include <cmath>
#include <bitset>
#include <utility>
#include <set>
#include <numeric>
#include <ctime>

#define Inf 2147483647
#define Pi acos(-1.0)
#define N 50000
#define LL long long

#define F(i, a, b) for( int i = (a); i < (b); i++ )
#define Fs(i, sz) for( size_t i = 0; i < sz.size (); i++ )
#define Fe(it, x) for(typeof (x.begin()) it = x.begin(); it != x.end (); it++)
#define Pr(x) for(typeof (x.begin()) it = x.begin(); it != x.end (); it++) cout << *it << " "; cout << endl;
#define Set(a, s) memset(a, s, sizeof (a))
#define Rd(r) freopen(r, "r", stdin)
#define Wt(w) freopen(w, "w", stdout)

using namespace std;

enum State {UnLocked, Locked, SecureLocked};

LL dp [65 + 3] [3 + 2] [65 + 3];
int n, s;

LL recur (int at, State pre, int cntSecure)
{
	if ( at == n ) return cntSecure == s ? 1 : 0;

	if ( dp [at] [pre] [cntSecure] != -1 ) return dp [at] [pre] [cntSecure];

	LL c = 0;

	if ( pre == UnLocked ) {
		c += recur (at + 1, UnLocked, cntSecure);
		c += recur (at + 1, Locked, cntSecure);
	} else if ( pre == Locked ) {
		c += recur (at + 1, UnLocked, cntSecure);
		c += recur (at + 1, SecureLocked, cntSecure + 1);
	} else {
		c += recur (at + 1, UnLocked, cntSecure);
		c += recur (at + 1, SecureLocked, cntSecure + 1);
	}

	return dp [at] [pre] [cntSecure] = c;
}

int main ()
{
	while ( scanf ("%d %d", &n, &s) ) {
		if ( n < 0 && s < 0 ) break;

		Set (dp, -1);

		printf ("%lld\n", recur (0, Locked, 0));
	}

	return 0;
}

// @END_OF_SOURCE_CODE

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