Create Day 21 Count Square Submatrices with All Ones.cpp

Author: tusharjaiswal123

Day 21 Count Square Submatrices with All Ones.cpp

@@ -0,0 +1,75 @@
+PROBLEM:
+
+
+
+Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.
+
+
+Example 1:
+Input: matrix =
+[
+  [0,1,1,1],
+  [1,1,1,1],
+  [0,1,1,1]
+]
+Output: 15
+Explanation: 
+There are 10 squares of side 1.
+There are 4 squares of side 2.
+There is  1 square of side 3.
+Total number of squares = 10 + 4 + 1 = 15.
+
+Example 2:
+Input: matrix = 
+[
+  [1,0,1],
+  [1,1,0],
+  [1,1,0]
+]
+Output: 7
+Explanation: 
+There are 6 squares of side 1.  
+There is 1 square of side 2. 
+Total number of squares = 6 + 1 = 7.
+ 
+
+Constraints:
+
+1. 1 <= arr.length <= 300
+2. 1 <= arr[0].length <= 300
+3. 0 <= arr[i][j] <= 1
+
+
+
+
+SOLUTION:
+
+
+
+class Solution {
+public:
+    int countSquares(vector<vector<int>>& matrix) {
+        
+        int i,j,n,m,ans=0;
+        n=matrix.size();
+        m=matrix[0].size();
+        
+        vector<vector<int>> dp(n,vector<int>(m,0));
+        
+        for(i=0;i<n;i++)
+        {
+            for(j=0;j<m;j++)
+            {   
+               if( (i==0 || j==0 ) && matrix[i][j]==1)
+                   dp[i][j]=1;
+                else if(matrix[i][j]==1)
+                    dp[i][j] = 1 +min({dp[i-1][j],dp[i][j-1],dp[i-1][j-1]});
+                
+                ans+=dp[i][j];
+            }
+        }
+        
+        return ans;
+        
+    }
+};