【IOI 1994】 The Buses

【题目链接】

http://poj.org/problem?id=1167

【算法】

深度优先搜索 + 迭代加深

【代码】

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 1010

struct info
{
        int opt,fir;
} b[MAXN];

int i,n,g,mx;
int a[MAXN],h[MAXN];

inline bool check()
{
        for (i = ; i <= g; i++)
        {
                if (b[i].opt == )
                        return false;
        }
        return true;
}
inline bool IDDFS(int dep,int m)
{
        int i,d,tmp,e;
        if (dep > n)
        {
                if (check())
                        return true;
                else return false;
        }
        if (h[a[dep]] <= ) return IDDFS(dep+,m);
        for (i = ; i <= m; i++)
        {
                if (b[i].opt == )
                {
                        d = a[dep] - b[i].fir;
                        if (d <= b[i].fir) continue;
                        b[i].opt = ;
                        tmp = a[dep];
                        while (tmp <= mx && h[tmp] > )
                        {
                                h[tmp]--;
                                tmp += d;
                        }
                        if (tmp > mx)
                        {
                                if (IDDFS(dep+,m))
                                        return true;
                        }
                        b[i].opt = ;
                        e = tmp - d;
                        tmp = a[dep];
                        while (tmp <= e)
                        {
                                h[tmp]++;
                                tmp += d;
                        }
                }
        }
        if (m >= g) return false;
        if ( * a[dep] >= ) return false;
        m++;
        h[a[dep]]--;
        b[m].opt = ;
        b[m].fir = a[dep];
        if (IDDFS(dep+,m))
                return true;
        h[a[dep]]++;
        return false;
}

int main()
{

        scanf("%d",&n);
        for (i = ; i <= n; i++)
        {
                scanf("%d",&a[i]);
                if (a[i] > mx)
                        mx = a[i];
                h[a[i]]++;
        }
        for (i = ; i <= ; i++)
        {
                g = i;
                if (IDDFS(,))
                        break;
        }
        printf("%d\n",g);

        return ;

}