UVa 12462 - Rectangle Solution

#include<iostream>
#include<list>
#include<string>
#include<cstring>
#include<sstream>
#include<cctype>
#include<string.h>
#include<algorithm>
#include<cmath>
#include<stack>
#include<fstream>
#include<cstdlib>
#include<vector>
#include<map>
#include<utility>
#include<iomanip>
#include<queue>

using namespace std;

#define INF (1<<29)
#define SET(a) memset(a,-1,sizeof(a))
#define ALL(a) a.begin(),a.end()
#define CLR(a) memset(a,0,sizeof(a))
#define FILL(a,v) memset(a,v,sizeof(a))
#define PB push_back
#define FOR(i,n) for(int i = 0;i<n;i++)
#define PI acos(-1.0)
#define EPS 1e-9
#define MP(a,b) make_pair(a,b)
#define READ(f) freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)
#define LL long long
#define MX 100100


LL colorNum[MX][40];
LL n,c,t,kk=1,histogram[MX],i,lft[MX],rgt[MX],mx,color[MX];

int main()
{
    stack<LL>stk;
    while(cin>>n>>c &&n &&c)
    {
        for(i=1;i<=n;i++)
        scanf("%lld",&histogram[i]);

        CLR(colorNum);

        for(i=1;i<=n;i++)
        {
            scanf("%lld",&color[i]);
            long long cl=color[i];
            colorNum[i][cl]=(colorNum[i-1][cl])+1;

            for(int j=0;j<cl;j++)
            colorNum[i][j]=colorNum[i-1][j];
            for(int j=cl+1;j<c;j++)
            colorNum[i][j]=colorNum[i-1][j];

         }


        while(!stk.empty())
            stk.pop();

        stk.push(0);
        histogram[0]=0;

        for(i=1;i<=n;i++)
        {
            while(histogram[stk.top()]>=histogram[i])
                stk.pop();

             lft[i]=  stk.top()+1;
             stk.push(i);
        }

        while(!stk.empty())
            stk.pop();

        stk.push(n+1);
        histogram[n+1]=0;

        for(i=n;i>0;i--)
        {
            while(histogram[stk.top()]>=histogram[i])
                stk.pop();

             rgt[i]=  stk.top()-1;
             stk.push(i);
        }
        mx=0;
        for(i=1;i<=n;i++)
            {
                bool chk=true;;
                for(int j=0;j<c;j++)
                    if(colorNum[rgt[i]][j] - colorNum[lft[i]-1][j]==0)
                        chk=false;
                if(chk)
                mx=max(mx,(rgt[i]-lft[i]+1)*histogram[i]);
            }
          cout<<mx<<endl;
        }
return 0;
}