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largestrectangle.cpp
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largestrectangle.cpp
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class Solution {
public:
struct point{
int h;
int p;
};
int largestRectangleArea(vector<int> &height) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int x[50000],y[50000];
int newh;
memset(x,0,sizeof(x));
memset(y,0,sizeof(y));
stack<point> s;
for(int i = 0; i < height.size(); i ++){
newh = height[i];
while(!s.empty()){
point cmppoint = s.top();
if(cmppoint.h >= newh){
s.pop();
}
else{
break;
}
}
if(s.empty()){
x[i] = 0;
}
else{
x[i] = s.top().p +1;
}
point newpoint;
newpoint.h = newh;
newpoint.p = i;
s.push(newpoint);
}
while(!s.empty())
s.pop();
for(int i = height.size()-1; i >= 0; i --){
newh = height[i];
while(!s.empty()){
point cmppoint = s.top();
if(cmppoint.h >= newh){
s.pop();
}
else{
break;
}
}
if(s.empty()){
y[i] = height.size() -1;
}
else{
y[i] = s.top().p-1;
}
point newpoint;
newpoint.h = newh;
newpoint.p = i;
s.push(newpoint);
}
int maxarea = 0;
for(int i = 0; i < height.size(); i ++){
int length = y[i]-x[i]+1;
if(length * height[i] > maxarea)
maxarea = length * height[i];
}
return maxarea;
}
};