POJ.2082 Terrible Sets

1.Problem
2082 -- Terrible Sets (poj.org)

2.Idea
Description is terrible but it was just simple max rectangle in histogram problem.

3.Source

 int n;  
 int h[N];  
 int st[N], L[N], R[N], sum[N];  
 int maxRec() {  
      //L   
      int t = 0;  
      for (int i = 0; i < n; i++) {  
           while (t > 0 && h[st[t - 1]] >= h[i]) t--;  
           L[i] = (t == 0 ? 0 : (st[t - 1] + 1));  
           st[t++] = i;  
      }  
      //R   
      t = 0;  
      for (int i = n - 1; i >= 0; i--) {  
           while (t > 0 && h[st[t - 1]] >= h[i]) t--;  
           R[i] = (t == 0 ? n : st[t - 1]);  
           st[t++] = i;  
      }  
      int res = 0;  
      for (int i = 0; i < n; i++) {  
           res = max(res, h[i] * (sum[R[i]] - sum[L[i]]));  
      }  
      return res;  
 }  
 void solve()  
 {  
      while (cin >> n) {  
           if (n < 0) break;  
           for (int i = 0; i < n; i++) {  
                scanf("%d%d", &sum[i + 1], &h[i]);  
           }  
           for (int i = 0; i < n; i++)   
                sum[i + 1] += sum[i];  
           printf("%d\n", maxRec());  
      }  
 }