01 Matrix

Author: nikoo28

src/main/java/leetcode/medium/UpdateMatrix.java

@@ -0,0 +1,39 @@
+package leetcode.medium;
+
+public class UpdateMatrix {
+
+  int[][] updateMatrix(int[][] mat) {
+    int rows = mat.length;
+    int cols = mat[0].length;
+    int[][] result = new int[rows][cols];
+
+    // Initialize the result matrix with maximum values
+    for (int i = 0; i < rows; i++)
+      for (int j = 0; j < cols; j++)
+        result[i][j] = Integer.MAX_VALUE;
+
+    // First pass: top-left to bottom-right
+    for (int i = 0; i < rows; i++)
+      for (int j = 0; j < cols; j++)
+        if (mat[i][j] == 0) result[i][j] = 0;
+        else {
+          if (i > 0)
+            result[i][j] = Math.min(result[i][j], result[i - 1][j] + 1);
+          if (j > 0)
+            result[i][j] = Math.min(result[i][j], result[i][j - 1] + 1);
+        }
+
+    // Second pass: bottom-right to top-left
+    for (int i = rows - 1; i >= 0; i--)
+      for (int j = cols - 1; j >= 0; j--)
+        if (mat[i][j] != 0) {
+          if (i < rows - 1)
+            result[i][j] = Math.min(result[i][j], result[i + 1][j] + 1);
+          if (j < cols - 1)
+            result[i][j] = Math.min(result[i][j], result[i][j + 1] + 1);
+        }
+
+    return result;
+  }
+
+}

src/test/java/leetcode/medium/UpdateMatrixTest.java

@@ -0,0 +1,44 @@
+package leetcode.medium;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class UpdateMatrixTest {
+
+  private final UpdateMatrix updateMatrix;
+
+  UpdateMatrixTest() {
+    updateMatrix = new UpdateMatrix();
+  }
+
+  @Test
+  void testUpdateMatrix1() {
+    int[][] mat = {
+        {0, 0, 0},
+        {0, 1, 0},
+        {1, 1, 1}
+    };
+    int[][] expected = {
+        {0, 0, 0},
+        {0, 1, 0},
+        {1, 2, 1}
+    };
+    assertArrayEquals(expected, updateMatrix.updateMatrix(mat));
+  }
+
+  @Test
+  void testUpdateMatrix2() {
+    int[][] mat = {
+        {0, 0, 0},
+        {0, 1, 0},
+        {1, 1, 1}
+    };
+    int[][] expected = {
+        {0, 0, 0},
+        {0, 1, 0},
+        {1, 2, 1}
+    };
+    assertArrayEquals(expected, updateMatrix.updateMatrix(mat));
+  }
+}