Create LargestSquareSubMatrixOf1.java

Author: 17tanya

DynamicProgramming/LargestSquareSubMatrixOf1.java

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+/*
+https://www.techiedelight.com/find-size-largest-square-sub-matrix-1s-present-given-binary-matrix/
+
+*/
+
+//Bottom up DP
+
+public int maxSizeOfSquareSubMatrix(int A[][]){
+    int n = A.length;
+    int m = A[0].length;
+    
+    //dp[i][j] indicates the side-length of the largest square sub-matrix formed when (i,j) is the bottom-right corner of that sub-matrix
+    int dp[][] = new int[n][m];
+    
+    int maxSize = 0;
+    
+    for(int i=0;i<n;i++){
+        for(int j=0;j<m;j++){
+        
+            dp[i][j] = A[i][j];
+            
+            //if we are not in the first row or column and the current element is 1, then check for sub-matrix
+            if(i>0 && j>0 && A[i][j]==1){
+                //dp[i-1][j] --> Top cell
+                //dp[i][j-1] --> left cell
+                //dp[i-1][j-1] --> top left cell
+                //we chose the minimum value because it is the LIMITING VALUE and we can not have a square sub-matrix
+                //of length greater than this minimum value
+                dp[i][j] = Math.min(dp[i-1][j], dp[i][j-1], dp[i-1][j-1]) + 1;
+            }
+            
+            maxSize = Math.max(maxSize, dp[i][j]);
+        }
+    }
+    
+    return maxSize;
+    
+}
+
+/*
+Time and Space Complexity - O(n*m)
+*/