luogu P1120 小木棍 ［数据加强版］

二次联通门 : luogu P1120 小木棍 ［数据加强版］

/*
    luogu P1120 小木棍 ［数据加强版］
    
    暴搜 + 剪枝
     
    枚举可能的长度
    挨个检查答案 
    二分显然正确性不能保障
     
    搜索时从最大的开始找
        放上当前木棍后的长度比枚举的长度要大， 则退出 
        
        若当前的长度与当前扫到的木棍长度相同，
        或是还需要的长度与枚举的长度相同，则退出 
         
        若当前的木棍不符合要求， 则后面与它长度相同的木棍都不行
          
*/
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>

#define INF 1e7

#define Max 300

using namespace std;

void read (int &now)
{
    now = 0;
    char word = getchar ();
    while (word > '9' || word < '0')
        word = getchar ();
    while (word >= '0' && word <= '9')
    {
        now = now * 10 + word - '0';
        word = getchar ();
    }
}


bool Comp (int a, int b)
{
    return a > b;
}

int N;
int length[Max];
int Count;
int Answer;
int Len;

inline int max (int a, int b)
{
    return a > b ? a : b;
}

int Limit, Need;
int Total;
bool visit[Max];

bool Dfs (int now, int Len, int number)
{
    if (number == Total)
    {
        Answer = Need;
        return true;
    }
    if (Len == 0)
        if (Dfs (1, Need, number + 1))
            return true;
    for (int i = now; i <= N; i++)
        if (!visit[i] && length[i] <= Len)
        {
            visit[i] = true;
            if (Dfs (i + 1, Len - length[i], number))
                return true;
            visit[i] = false;
            if (Len == length[i] || Len == Need)
                break;
            while (length[i] == length[i + 1])
                i++;
        }
    return false;
}

int main (int argc, char *argv[])
{
    int x, res;
    read (res);
    for (int i = 1; i <= res; i++)
    {        
        read (x);
        if (x <= 100)
        {
            length[++N] = x;
            Limit += x;
            Need = max (x, Need);
        }
    }
    sort (length + 1, length + 1 + N, Comp);
    for (; Need <= Limit; Need++)
        if (Limit % Need == 0)
        {
            Total = Limit / Need;
            if (Dfs (1, Need, 0))
                break;
        }
    printf ("%d", Answer);
    return 0;
}