Create 329-Longest-Increasing-Path-in-a-Matrix.java

Author: SharmaTushar1

java/329-Longest-Increasing-Path-in-a-Matrix.java

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+//Another similar problem: https://leetcode.com/contest/weekly-contest-300/problems/number-of-increasing-paths-in-a-grid/
+
+class Solution {
+    public int longestIncreasingPath(int[][] matrix) {
+        int m = matrix.length;
+        int n = matrix[0].length;
+        int[][] dp = new int[m][n];
+        for (int d[]: dp) 
+            Arrays.fill(d, -1);
+        for (int i = 0; i<m; i++) {
+            for (int j = 0; j<n; j++) {
+                if (dp[i][j]==-1)
+                    dfs(matrix, dp, m, n, i, j, -1);
+            }
+        }
+        int max = Integer.MIN_VALUE;
+        for (int[] d: dp) {
+            for (int i: d) 
+                max = Math.max(i, max);
+        }
+        return max;
+    }
+    
+    public int dfs(int[][] matrix, int[][] dp, int m, int n, int i, int j, int parent) {
+        if (i>=m || j>=n || i<0 || j<0 || matrix[i][j]<=parent) 
+            return 0;
+        parent = matrix[i][j];
+        if (dp[i][j]!=-1)
+            return dp[i][j];
+        int left = dfs(matrix, dp, m, n, i, j-1, parent);
+        int right = dfs(matrix, dp, m, n, i, j+1, parent);
+        int bottom = dfs(matrix, dp, m, n, i+1, j, parent);
+        int top = dfs(matrix, dp, m, n, i-1, j, parent);
+        dp[i][j] = 1+Math.max(Math.max(left, right), Math.max(top, bottom));
+        return dp[i][j];
+    }
+}