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Histogram.cpp
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Histogram.cpp
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#include <Iostream>
using namespace std;
vector<int> Smallest(vector<int> heights, int n)
{
vector<int> ps(n);
stack<int> st;
for (int i = 0; i < n; i++)
{
while (!st.empty() && heights[st.top()] >= heights[i])
{
st.pop();
}
if (st.empty())
{
ps[i] = -1;
}
else
{
ps[i] = st.top();
}
st.push(i);
}
return ps;
}
vector<int> newSmallest(vector<int> heights, int n)
{
vector<int> ns(n);
stack<int> st;
for (int i = n - 1; i >= 0; i--)
{
while (!st.empty() && heights[st.top()] >= heights[i])
{
st.pop();
}
if (st.empty())
{
ns[i] = -1;
}
else
{
ns[i] = st.top();
}
st.push(i);
}
return ns;
}
int area(vector<int> heights)
{
int n = heights.size();
vector<int> ps(n);
vector<int> ns(n);
ps = Smallest(heights, n);
ns = newSmallest(heights, n);
int max_ans = 0;
for (int i = 0; i < n; i++)
{
int curr = (ns[i] - ps[i] - 1) * heights[i]; // Main Formula
max_ans = max(max_ans, curr);
}
return max_ans;
}
int main()
{
vector<int> heights{4, 6, 8, 2, 5, 7, 9};
// heights.push_back(1);
// heights.push_back(2);
// heights.push_back(3);
// int n = heights.size();
// cout << n;
cout << heights[2];
cout << "The area: " << area(heights) << endl;
return 0;
}