蓝桥集训之矩形牛棚

• 核心思想：单调队列

  • 模板：Acwing.131.直方图矩形面积
  • 首先遍历所有下界 然后确定以该下界为底的直方图 求最大矩形
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•   #include <iostream>#include <cstring>#include <algorithm>using namespace std;const int N = 3010;int stk[N],top;int r[N],l[N];int g[N][N],h[N][N];int n,m,q;int work(int h[])  //找最大面积{top = 0;stk[++top] = 0;  //边界下标加入h[0] = h[m+1] = -1;  //左右边界for (int i = 1; i <= m; i ++ ){while (h[stk[top]] >= h[i]) top -- ;  //h[i]更优l[i] = stk[top];  //l[i]为左边第一个比h[i]小的stk[ ++ top] = i;}top = 0;stk[++top] = m+1;  //右边界下标for (int i = m; i; i -- ){while (h[stk[top]] >= h[i]) top -- ;r[i] = stk[top];  //r[i]为右边第一个比h[i]小的stk[ ++ top] = i;}int res=0;for(int i=1;i<=m;i++)res = max(res,h[i] * (r[i] - l[i] - 1));  //长乘宽return res;}int main(){cin>>n>>m>>q;while(q--){int x,y;cin>>x>>y;g[x][y] = 1;}for (int i = 1; i <= n; i ++ )for (int j = 1; j <= m; j ++ )if(!g[i][j])  //如果没有被破坏h[i][j] = h[i-1][j] + 1;  //递归求h数组int res=0;for (int i = 1; i <=n; i ++ )res = max(res , work(h[i]));cout<<res<<endl;}