Sticks

来源：互联网发布：mysql 取一条记录编辑：程序博客网时间：2024/06/05 22:36

http://acm.nyist.net/JudgeOnline/problem.php?pid=293

#include <cstdio>
#include <algorithm>
using std::sort;
int stick[66], n, sum, len, ok, temp;
bool vis[66];

bool cmp(int a, int b)

{
return a > b;
}

bool DFS(int k, int left, int total)

{ //第k个木棍，剩下的匹配长度，剩下的总长度
if(left == 0)

{ //已经匹配完一份
  total -= len;
  if(!total) return true;

  int i = 1;
  while(vis[i]) ++i;
  vis[i] = 1; //cut, 找到的第一根肯定要用，此时就给他用掉，如果不用会TLE
  if(DFS(i + 1, len - stick[i], total)) return true;
  vis[i] = 0;
  return false;
}

for(int i = k; i < n; ++i)

{
  if(i > 0 && stick[i] == stick[i-1] && !vis[i-1]) //cut,若前一个相同长度的匹配失效，则当前不需要深搜下去
   continue;
  if(!vis[i] && left >= stick[i])

{
   vis[i] = 1; left -= stick[i];
   if(DFS(i + 1, left, total)) return true;
   vis[i] = 0;
   if(!left) return false; //cut
   left += stick[i];
  }
}
return false;
}

int main()

{
while(scanf("%d", &n), n)

{
sum = ok = 0;
for(int i = 0; i < n; ++i)

{
   scanf("%d", stick + i);
   vis[i] = 0; sum += stick[i];
  }
  sort(stick, stick + n, cmp);
  temp = sum / 2; len = stick[0]; //剪枝1
  vis[0] = 1;
  while(len <= temp)

{
if(sum % len == 0 && DFS(1, len - stick[0], sum))

{ //剪枝2
    printf("%d\n", len);
    ok = 1; break;
   }
   ++len;
  }
  if(!ok) printf("%d\n", sum);
}
return 0;
}

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