From 2df05e4971c75cde09b2f5fb9961cd2d4bf6858b Mon Sep 17 00:00:00 2001
From: PrakarshKamal <kamalp@mcmaster.ca>
Date: Tue, 10 Mar 2026 20:47:31 -0400
Subject: [PATCH] Complete DFS-1

---
 01Matrix.java  | 48 +++++++++++++++++++++++++++++++++++
 FloodFill.java | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+)
 create mode 100644 01Matrix.java
 create mode 100644 FloodFill.java

diff --git a/01Matrix.java b/01Matrix.java
new file mode 100644
index 00000000..dd23cd97
--- /dev/null
+++ b/01Matrix.java
@@ -0,0 +1,48 @@
+import java.util.*;
+
+// BFS O(n * m) time, O(n * m) space
+class Solution {
+    public int[][] updateMatrix(int[][] mat) {
+        int n = mat.length;
+        int m = mat[0].length;
+
+        int[][] dirs = new int[][] {
+            {0,1},{1,0},{-1,0},{0,-1}
+        };
+
+        Queue<int[]> q = new LinkedList<>();
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if (mat[i][j] == 0) {
+                    q.offer(new int[]{i, j});
+                }
+                else {
+                    mat[i][j] = -1;
+                }
+            }
+        }
+
+        int distance = 1;
+
+        while (!q.isEmpty()) {
+            int size = q.size();
+
+            for (int i = 0; i < size; i++) {
+                int[] curr = q.poll();
+                for (int[] dir : dirs) {
+                    int r = curr[0] + dir[0];
+                    int c = curr[1] + dir[1];
+
+                    if (r >= 0 && c >= 0 && r < n && c < m && mat[r][c] == -1) {
+                        q.offer(new int[] {r,c});
+                        mat[r][c] = distance;
+                    }
+                }
+                
+            }
+            distance++;
+        }
+        return mat;
+    }
+}
diff --git a/FloodFill.java b/FloodFill.java
new file mode 100644
index 00000000..0c23aaab
--- /dev/null
+++ b/FloodFill.java
@@ -0,0 +1,68 @@
+// BFS O(n * m) time, O(n * m) space
+// class Solution {
+//     public int[][] floodFill(int[][] image, int sr, int sc, int color) {
+//         int n = image.length;
+//         int m = image[0].length;
+
+//         int[][] dirs = new int[][] {
+//             {0,1},{1,0},{-1,0},{0,-1}
+//         };
+
+//         int oldColor = image[sr][sc];
+
+//         if (oldColor == color) return image;
+
+//         Queue<int[]> q = new LinkedList<>();
+//         q.offer(new int[] {sr, sc});
+//         image[sr][sc] = color;
+
+//         while (!q.isEmpty()) {
+//             int[] curr = q.poll();
+
+//             for (int[] dir : dirs) {
+//                 int r = curr[0] + dir[0];
+//                 int c = curr[1] + dir[1];
+
+//                 if (r >= 0 && c >= 0 && r < n && c < m && image[r][c] == oldColor) {
+//                     q.offer(new int[] {r, c});
+//                     image[r][c] = color;
+//                 }
+//             }
+//         }
+//         return image;
+//     }
+// }
+
+// DFS O(n * m) time, O(n * m) space
+class Solution {
+    public int[][] floodFill(int[][] image, int sr, int sc, int color) {
+        int n = image.length;
+        int m = image[0].length;
+
+        int[][] dirs = new int[][] {
+            {0,1},{1,0},{-1,0},{0,-1}
+        };
+
+        int oldColor = image[sr][sc];
+
+        if (oldColor == color) return image;
+
+        dfs(image, sr, sc, n, m, dirs, oldColor, color);
+        
+        return image;
+    }
+
+    private void dfs(int[][] image, int i, int j, int n, int m, int[][] dirs, int oldColor, int color) {
+        
+        image[i][j] = color;
+
+        for (int[] dir : dirs) {
+            int r = i + dir[0];
+            int c = j + dir[1];
+
+            if (r >= 0 && c >= 0 && r < n && c < m && image[r][c] == oldColor) {
+                dfs(image, r, c, n, m, dirs, oldColor, color);
+            }
+        }
+    }
+}
\ No newline at end of file