matrix question(c++)

Author: Ishasingh006

cpp_matrix/Max_rectangle.cpp

@@ -0,0 +1,85 @@
+/*Given a binary matrix M of size n X m. Find the
+ maximum area of a rectangle formed only of 1s in 
+ the given matrix.*/
+#include <bits/stdc++.h>
+using namespace std;
+#define MAX 1000
+
+
+
+class Solution{
+  public:
+    int minareahistogram(int a[],int m)
+    {
+        int pres[m],nexts[m];
+        stack<pair<int,int>> s,q;
+        
+        for(int i=0;i<m;i++)
+        {   
+            while(s.size()!=0 && s.top().first>=a[i])
+            {
+                s.pop();
+            }
+            if(s.size()==0)
+            pres[i]=0;
+            else
+            pres[i]=s.top().second;
+            s.push({a[i],i+1});
+        }
+        for(int i=m-1;i>=0;i--)
+        {
+            while(!q.empty() && q.top().first>=a[i])
+            {
+                q.pop();
+            }
+            if(q.empty())
+            nexts[i]=m+1;
+            else
+            nexts[i]=q.top().second;
+            q.push({a[i],i+1});
+        }
+        int ma=0;
+        for(int i=0;i<m;i++)
+        {   int p=nexts[i]-pres[i]-1;
+            ma=max(ma,a[i]*p);
+        }
+        return ma;
+    }
+    int maxArea(int m[MAX][MAX], int n, int m1) {
+        int a[m1]={0},ma=0;
+        for(int i=0;i<n;i++)
+        {
+            for(int j=0;j<m1;j++)
+            {
+                if(m[i][j]==0)
+                a[j]=m[i][j];
+                else
+                a[j]+=m[i][j];
+            }
+            ma=max(ma,minareahistogram(a,m1));
+        }
+        return ma;
+    }
+    
+};
+
+
+int main() {
+    int T;
+    cin >> T;
+
+    int M[MAX][MAX];
+
+    while (T--) {
+        int n, m;
+        cin >> n >> m;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                cin >> M[i][j];
+            }
+        }
+        Solution obj;
+        cout << obj.maxArea(M, n, m) << endl;
+    }
+}

cpp_matrix/Median_row-wise_sorted_Matrix.cpp

@@ -0,0 +1,49 @@
+//Median in a row-wise sorted Matrix
+#include <bits/stdc++.h>
+using namespace std;
+
+
+class Solution{   
+public:
+    int check(vector<vector<int>> &matrix,int m)
+    {   int c=0;
+        for(int i=0;i<matrix.size();i++)
+        {
+            int p=upper_bound(matrix[i].begin(),matrix[i].end(),m)-matrix[i].begin();
+            c+=p;
+        }
+        return c;
+    }
+    int median(vector<vector<int>> &matrix, int r, int c){
+          int l=1,r1=2000;
+          while(l<=r1)
+          {
+              int mid=(r1+l)/2;
+              int p=check(matrix,mid);
+              if(p<=(r*c)/2)
+              l=mid+1;
+              else
+              r1=mid-1;
+          }
+          return l;
+    }
+};
+
+
+int main()
+{
+    int t;
+    cin>>t;
+    while(t--)
+    {
+        int r, c;
+        cin>>r>>c;
+        vector<vector<int>> matrix(r, vector<int>(c));
+        for(int i = 0; i < r; ++i)
+            for(int j = 0;j < c; ++j)
+                cin>>matrix[i][j];
+        Solution obj;
+        cout<<obj.median(matrix, r, c)<<endl;        
+    }
+    return 0;
+}

cpp_matrix/Row_with_max_1s.cpp

@@ -0,0 +1,41 @@
+//Row with max 1s
+#include <bits/stdc++.h>
+using namespace std;
+
+
+class Solution{
+public:
+	int rowWithMax1s(vector<vector<int> > arr, int n, int m) {
+	   int i=0,j=m-1,r=-1;
+	   
+	   while(i<n && j>=0)
+	   {while(arr[i][j]==1)
+	   {
+	       j--;
+	       r=i;
+	   }
+	   i++;
+       }
+      return r;
+	}
+
+};
+
+int main() {
+    int t;
+    cin >> t;
+    while (t--) {
+        int n, m;
+        cin >> n >> m;
+        vector< vector<int> > arr(n,vector<int>(m));
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                cin>>arr[i][j];
+            }
+        }
+        Solution ob;
+        auto ans = ob.rowWithMax1s(arr, n, m);
+        cout << ans << "\n";
+    }
+    return 0;
+}