I learned a new and nice technique from this one and it is a high thinking and time killing problem.
/* user: turing_13 link: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&amp;Itemid=8&amp;page=show_problem&amp;category=24&amp;problem=3905&amp;mosmsg=Submission+received+with+ID+14810702 */ #include <bits/stdc++.h> #define pii pair <int,int> #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<<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("%d",&a) #define loop(i,n) for(int i=0;i<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<<pos;} bool check(int n,int pos) { return n & 1<<pos;} int Reset(int n, int pos) { return n=n & ~(1<<pos);} /* ---------End of Header---------0*/ ll hight[MAX],color[MAX],ans[MAX]; int main() { ///freopen("in.txt","r",stdin); ///freopen("out.txt","w",stdout); int n,c; while(cin>>n>>c && n) { for(int i=1;i<=n;i++) cin>>hight[i]; for(int i=1;i<=n;i++) { int j; cin>>j; color[i]=1<<j; } hight[0]=hight[n+1]=0; color[0]=color[n+1]=0; /* Left to Right Check */ { stack<int>stk; stk.push(0); for(int i=1;i<=n;i++) { while(hight[stk.top()]>=hight[i]) { color[i]|=color[stk.top()]; stk.pop(); } ans[i]=(i-stk.top())*hight[i]; stk.push(i); } } /* Right to Left Check */ { stack<int>stk; stk.push(n+1); for(int i=n;i>0;i--) { while(hight[stk.top()]>=hight[i]) { color[i]|=color[stk.top()]; stk.pop(); } ans[i]+=(stk.top()-i)*hight[i]; stk.push(i); } } for(int i=1;i<=n;i++) ans[i]-=hight[i]; int ans_color=(1<<c)-1; ll max_ans=0; for(int i=1;i<=n;i++) if(color[i]==ans_color) max_ans=max(max_ans,ans[i]); cout<<max_ans<<endl; } return 0; }