Add 329_Longest_Increasing_Path_in_a_Matrix.java

Author: Sean Prashad

Tree Depth First Search/329_Longest_Increasing_Path_in_a_Matrix.java

@@ -0,0 +1,45 @@
+class Solution {
+    private static final int[][] dirs = { { 0, -1 }, { 0, 1 }, { -1, 0 }, { 1, 0 } };
+
+    public int longestIncreasingPath(int[][] matrix) {
+        if (matrix == null || matrix.length == 0) {
+            return 0;
+        }
+
+        int result = 0;
+
+        int[][] cache = new int[matrix.length][matrix[0].length];
+
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix[i].length; j++) {
+                result = Math.max(result, dfs(matrix, i, j, cache));
+            }
+        }
+
+        return result;
+    }
+
+    private int dfs(int[][] matrix, int x, int y, int[][] cache) {
+        if (cache[x][y] != 0) {
+            return cache[x][y];
+        }
+
+        int max = 1;
+
+        for (int[] dir : dirs) {
+            int nextX = dir[0] + x;
+            int nextY = dir[1] + y;
+
+            if (nextX < 0 || nextX >= matrix.length || nextY < 0 || nextY >= matrix[0].length
+                    || matrix[nextX][nextY] <= matrix[x][y]) {
+                continue;
+            }
+
+            int len = 1 + dfs(matrix, nextX, nextY, cache);
+            max = Math.max(max, len);
+        }
+
+        cache[x][y] = max;
+        return max;
+    }
+}