Day 21 Solution

Author: vamsikrish53

May LeetCoding Challenge/Day_ 21/Solution.java

@@ -0,0 +1,38 @@
+// https://leetcode.com/problems/count-square-submatrices-with-all-ones/
+
+class Solution {
+ public int countSquares(int[][] matrix) {
+ int mat[][] = new int[matrix.length + 1][matrix[0].length + 1];
+ int sum = 0;
+ 
+ /* We can do Dynamic Programming by saving how many
+ Squares can be formed using the bottom right corner
+ element.
+ */
+ 
+ for(int i = 1; i <= matrix.length; i++)
+ for(int j = 1; j <= matrix[0].length; j++)
+ if(matrix[i - 1][j - 1] != 0)
+ sum += (mat[i][j] = Math.min(Math.min(mat[i - 1][j], mat[i][j - 1]), mat[i - 1][j - 1]) + 1);
+ 
+ 
+ /*
+ Workin on the first example:
+ ===========================
+ Matrix =
+ [0,1,1,1],
+ [1,1,1,1],
+ [0,1,1,1]
+ ===========================
+ mat after algorithm = 
+ [0,0,0,0,0],
+ [0,0,1,1,1],
+ [0,1,1,2,2],
+ [0,0,1,2,3]
+ ===========================
+ After summing all indicies, now we get the correct answer!
+ */
+ 
+ return sum;
+ }
+}