solves maximal square in java

Author: anishLearnsToCode

src/MaximalSquare.java

@@ -0,0 +1,64 @@
+// https://leetcode.com/problems/maximal-square
+// T: O(m * n)
+// S: O(m * n)
+
+public class MaximalSquare {
+    public int maximalSquare(char[][] matrix) {
+        final int rows = matrix.length, columns = matrix[0].length;
+        final int[][] dp = new int[rows][columns];
+
+        assignFirstRowInDPMatrix(dp, matrix);
+        assignFirstColumnInDPMatrix(dp, matrix);
+
+        int maxSideLen = contains1(dp) ? 1 : 0;
+
+        for (int row = 1 ; row < rows ; row++) {
+            for (int column = 1 ; column < columns ; column++) {
+                if (isOne(matrix[row][column])) {
+                    dp[row][column] = min(dp[row - 1][column], dp[row][column - 1], dp[row - 1][column - 1]) + 1;
+                } else dp[row][column] = 0;
+                maxSideLen = Math.max(maxSideLen, dp[row][column]);
+            }
+        }
+
+        return maxSideLen * maxSideLen;
+    }
+
+    private boolean contains1(int[][] dp) {
+        return contains1InFirstRow(dp) || contains1InFirstColumn(dp);
+    }
+
+    private boolean contains1InFirstRow(int[][] dp) {
+        for (int element : dp[0]) {
+            if (element == 1) return true;
+        }
+        return false;
+    }
+
+    private boolean contains1InFirstColumn(int[][] dp) {
+        for (int[] row : dp) {
+            if (row[0] == 1) return true;
+        }
+        return false;
+    }
+
+    private boolean isOne(char character) {
+        return character == '1';
+    }
+
+    private int min(int a, int b, int c) {
+        return Math.min(a, Math.min(b, c));
+    }
+
+    private void assignFirstRowInDPMatrix(int[][] dp, char[][] matrix) {
+        for (int column = 0 ; column < matrix[0].length ; column++) {
+            dp[0][column] = matrix[0][column] - '0';
+        }
+    }
+
+    private void assignFirstColumnInDPMatrix(int[][] dp, char[][] matrix) {
+        for (int row = 0 ; row < matrix.length ; row++) {
+            dp[row][0] = matrix[row][0] - '0';
+        }
+    }
+}