Create 329. Longest Increasing Path in a Matrix

Author: khushi3004

329. Longest Increasing Path in a Matrix

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+class Solution {
+    int[][] dir = {{1,0}, {-1,0}, {0,1}, {0,-1}};
+    public int longestIncreasingPath(int[][] matrix) {
+        if(matrix == null || matrix.length == 0) return 0;
+        int m = matrix.length, n = matrix[0].length;
+        int[][] mem = new int[m][n];
+        int longestPath = 0;
+        
+        for(int i = 0; i < m; i++) {
+            for(int j = 0; j < n; j++) {
+                int path = dfs(matrix, m, n, i, j, mem);
+                longestPath = Math.max(path, longestPath);
+            }
+        }
+        
+        return longestPath;
+    }
+    
+    public int dfs(int[][] matrix, int m, int n, int i, int j, int[][] mem) {
+        if(mem[i][j] > 0) return mem[i][j];
+        int max = 0;
+        for(int[] d : dir) {
+            int x = i+d[0], y = j+d[1]; 
+            if(x >= 0 && y >= 0 && x < m && y < n && matrix[x][y] > matrix[i][j]) {
+                max = Math.max(max, dfs(matrix, m, n, x, y, mem));
+            }
+        }
+        mem[i][j] = max+1;
+        return max+1;
+    }
+}