Time: 771 ms (5.01%), Space: 81.4 MB (50.14%) - LeetHub

Author: vickyguptaa7

0084-largest-rectangle-in-histogram/0084-largest-rectangle-in-histogram.cpp

@@ -0,0 +1,54 @@
+class Solution {
+public:
+    vector<int>findNextSmallToRight(vector<int>&arr)
+    {
+        int n=arr.size();
+        vector<int>nextSmall(n);
+        stack<int>st;
+        for(int i=n-1;i>=0;i--)
+        {
+            while(!st.empty()&&arr[st.top()]>=arr[i])
+            {
+                st.pop();
+            }
+            if(!st.empty())
+                nextSmall[i]=st.top();
+            else 
+                nextSmall[i]=n;
+            st.push(i);
+        }
+        return nextSmall;
+    }
+    vector<int>findNextSmallToLeft(vector<int>&arr)
+    {
+        int n=arr.size();
+        vector<int>nextSmall(n);
+        stack<int>st;
+        for(int i=0;i<n;i++)
+        {
+            while(!st.empty()&&arr[st.top()]>=arr[i])
+            {
+                st.pop();
+            }
+            if(!st.empty())
+                nextSmall[i]=st.top();
+            else 
+                nextSmall[i]=-1;
+            st.push(i);
+        }
+        return nextSmall;
+    }
+    
+    int largestRectangleArea(vector<int>& heights) {
+        vector<int>nextSmallToLeft=findNextSmallToLeft(heights);
+        vector<int>nextSmallToRight=findNextSmallToRight(heights);
+        int largestRectangle=0;
+        for(int i=0;i<heights.size();i++)
+        {
+            int length=nextSmallToRight[i]-nextSmallToLeft[i]-1;
+            cout<<length<<"\n";
+            largestRectangle=max(largestRectangle,length*heights[i]);
+        }
+        return largestRectangle;
+    }
+};