히스토그램에서 가장 큰 직사각형 영역을 찾는 C++ 프로그램

히스토그램에서 가장 큰 직사각형 영역을 찾는 C++ 프로그램입니다.

알고리즘 함수 getArea():

Begin
   Create an empty stack.
   Initialize the largest_area.
   Do a while loop start from first bar for every bar hist[i], where i = 0 to
      less than n:
   If stack is empty or hist[i] is higher than the bar at top of stack, then
      push ‘i’ to stack.
   Else
      this bar is smaller than the top of stack, then keep removing the
      top of stack while top of the stack is greater. Calculate area of
      rectangle with smallest bar. Element before top in stack is left
      index and i is right index for the top.
   Pop the remaining bars from stack if stack is not empty and calculate
      area with every popped bar as the smallest bar.
End

예시 코드

#include<iostream>
#include<stack>
using namespace std;
int getArea(int hist[], int n)
{
   stack<int> st;
   int largest_area = 0;
   int top;
   int toparea;
   int i = 0;
   while (i < n)
   {
      if (st.empty() || hist[st.top()] <= hist[i])
      st.push(i++);
      else
      {
         top = st.top();
         st.pop();
         toparea = hist[top] * (st.empty() ? i :
         i - st.top() - 1);
         if (largest_area < toparea)
         largest_area = toparea;
      }
   }
   while (st.empty() == false)
   {
      top = st.top();
      st.pop();
      toparea = hist[top] * (st.empty() ? i :
      i - st.top() - 1);
      if (largest_area < toparea)
      largest_area = toparea;
   }
   return largest_area;
}
int main()
{
   int hist[] = {6,7,4,5,3,2};
   int n = sizeof(hist)/sizeof(hist[0]);
   cout << "Largest area is " << getArea(hist, n);
   return 0;
}

출력

Largest area is 16