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Largest Area in Histogram.cpp
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Largest Area in Histogram.cpp
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class Solution {
public:
int largestRectangleArea(vector<int>& heights) {
stack<int>s,s2;
int n=heights.size();
int area= -1;
vector<int>l(n),r(n);
for(int i=0;i<n;i++)
{
if(s.empty()) {s.push(i); l[i] = 0;}
else
{
while(!s.empty() and heights[s.top()]>=heights[i])
{
s.pop();
}
if(!s.empty())
l[i] = s.top() + 1;
else
l[i] = 0;
s.push(i);
}
}
for(int i=n-1;i>=0;i--)
{
if(s2.empty()) {s2.push(i); r[i] = n-1;}
else
{
while(!s2.empty() and heights[s2.top()]>=heights[i])
{
s2.pop();
}
if(!s2.empty())
r[i] = s2.top() - 1;
else
r[i] = n-1;
s2.push(i);
}
}
for(int i=0;i<n;i++)
{
area = max(area,(r[i]-l[i]+1)*heights[i]);
}
return area;
}
};