# (UVa) 12462 – Rectangle

I learned a new and nice technique from this one and it is a high thinking and time killing problem.

```
/*
user: turing_13
*/

#include &lt;bits/stdc++.h&gt;

#define pii pair &lt;int,int&gt;
#define sc scanf
#define pf printf
#define Pi 2*acos(0.0)
#define ms(a,b) memset(a, b, sizeof(a))
#define pb(a) push_back(a)
#define MP make_pair
#define oo 1&lt;&lt;29
#define dd double
#define ll long long
#define EPS 10E-10
#define ff first
#define ss second
#define MAX 100010
#define SZ(a) (int)a.size()
#define getint(a) scanf(&quot;%d&quot;,&amp;a)
#define loop(i,n) for(int i=0;i&lt;n;i++)
#define all(a) a.begin(),a.end()
#define intlim 2147483648
#define inf 1000000
#define rtintlim 46340
#define llim 9223372036854775808
#define rtllim 3037000499
#define ull unsigned long long
#define I int

using namespace std;

/* Bits operation */

int Set(int n,int pos)  { return n = n | 1&lt;&lt;pos;}
bool check(int n,int pos) { return n &amp; 1&lt;&lt;pos;}
int Reset(int n, int pos) { return n=n &amp; ~(1&lt;&lt;pos);}

ll hight[MAX],color[MAX],ans[MAX];

int main()
{
///freopen(&quot;in.txt&quot;,&quot;r&quot;,stdin);
///freopen(&quot;out.txt&quot;,&quot;w&quot;,stdout);

int n,c;

while(cin&gt;&gt;n&gt;&gt;c &amp;&amp; n)
{
for(int i=1;i&lt;=n;i++)
cin&gt;&gt;hight[i];
for(int i=1;i&lt;=n;i++)
{
int j;
cin&gt;&gt;j;
color[i]=1&lt;&lt;j;
}

hight[0]=hight[n+1]=0;
color[0]=color[n+1]=0;

/* Left to Right Check */
{
stack&lt;int&gt;stk;
stk.push(0);
for(int i=1;i&lt;=n;i++)
{
while(hight[stk.top()]&gt;=hight[i])
{
color[i]|=color[stk.top()];
stk.pop();
}
ans[i]=(i-stk.top())*hight[i];
stk.push(i);
}
}

/* Right to Left Check */
{
stack&lt;int&gt;stk;
stk.push(n+1);
for(int i=n;i&gt;0;i--)
{
while(hight[stk.top()]&gt;=hight[i])
{
color[i]|=color[stk.top()];
stk.pop();
}
ans[i]+=(stk.top()-i)*hight[i];
stk.push(i);
}
}

for(int i=1;i&lt;=n;i++)
ans[i]-=hight[i];

int ans_color=(1&lt;&lt;c)-1;
ll max_ans=0;

for(int i=1;i&lt;=n;i++)
if(color[i]==ans_color)
max_ans=max(max_ans,ans[i]);

cout&lt;&lt;max_ans&lt;&lt;endl;
}
return 0;
}

```