code done + unit tested

Author: Ram swaroop

src/me/ramswaroop/arrays/BooleanMatrix.java

@@ -0,0 +1,81 @@
+package me.ramswaroop.arrays;
+
+/**
+ * Created by IntelliJ IDEA.
+ *
+ * @author: ramswaroop
+ * @date: 9/11/15
+ * @time: 3:28 PM
+ * @see: http://www.geeksforgeeks.org/a-boolean-matrix-question/
+ */
+public class BooleanMatrix {
+
+    /**
+     * Given a boolean matrix mat[M][N] of size M X N, modify it such that
+     * if a matrix cell mat[i][j] is 1 (or true) then make all the cells of
+     * ith row and jth column as 1.
+     *
+     * @param a
+     */
+    public static void modifyBooleanMatrix(int[][] a) {
+        int rowFlag = 0, colFlag = 0;
+
+        // if a[i][j] is 1 then we make a[0][j] 1 and a[i][0] 1
+        for (int i = 0; i < a.length; i++) {
+            for (int j = 0; j < a[0].length; j++) {
+                if (i == 0 || j == 0) {
+                    if (a[i][0] == 1) {
+                        rowFlag = 1;
+                    }
+                    if (a[0][j] == 1) {
+                        colFlag = 1;
+                    }
+                } else if (a[i][j] == 1) {
+                    a[0][j] = 1;
+                    a[i][0] = 1;
+                }
+            }
+        }
+
+        // if a[0][j] is 1 or a[i][0] is 1 then a[i][j] is 1
+        for (int i = 1; i < a.length; i++) {
+            for (int j = 1; j < a[0].length; j++) {
+                if (a[0][j] == 1 || a[i][0] == 1) {
+                    a[i][j] = 1;
+                }
+            }
+        }
+
+        if (rowFlag == 1) {
+            for (int j = 0; j < a[0].length; j++) {
+                a[0][j] = 1;
+            }
+        }
+        if (colFlag == 1) {
+            for (int i = 0; i < a.length; i++) {
+                a[i][0] = 1;
+            }
+        }
+    }
+
+    private static void print2DMatrix(int[][] a) {
+        for (int i = 0; i < a.length; i++) {
+            for (int j = 0; j < a[0].length; j++) {
+                System.out.print(a[i][j]);
+            }
+            System.out.println();
+        }
+    }
+
+    public static void main(String a[]) {
+        int[][] ar = new int[][]{{1, 0, 0, 1}, {0, 0, 1, 0}, {0, 0, 0, 0}};
+        print2DMatrix(ar);
+        modifyBooleanMatrix(ar);
+        print2DMatrix(ar);
+        System.out.println("-------");
+        ar = new int[][]{{1, 0}, {0, 0}};
+        print2DMatrix(ar);
+        modifyBooleanMatrix(ar);
+        print2DMatrix(ar);
+    }
+}