January 19

Author: aliasvishnu

329-LongestIncreasingPathInAMatrix.cpp

@@ -0,0 +1,56 @@
+#define vvi vector<vector<int>>
+class Solution {
+public:
+    bool insideBounds(int i, int j, int rows, int cols){
+        return (i < rows && i >= 0) && (j < cols && j >= 0);
+    }
+
+    int DFS(vvi &matrix, int i, int j, int depth, vvi &DP, vvi &visit, int rows, int cols){
+        int maxDepth = depth;
+        if(DP[i][j] != -1) return depth+DP[i][j];
+        visit[i][j] = 1;
+
+
+        if(insideBounds(i+1, j, rows, cols) && visit[i+1][j] == 0 && matrix[i+1][j] > matrix[i][j]){
+           int d = (DP[i+1][j] == -1)? DFS(matrix, i+1, j, depth+1, DP, visit, rows, cols): depth+DP[i+1][j];
+           maxDepth = max(maxDepth, d);
+        }
+        if(insideBounds(i, j+1, rows, cols) && visit[i][j+1] == 0 && matrix[i][j+1] > matrix[i][j]){
+           int d =  (DP[i][j+1] == -1)? DFS(matrix, i, j+1, depth+1, DP, visit, rows, cols): depth+DP[i][j+1];
+           maxDepth = max(maxDepth, d);
+        }
+        if(insideBounds(i-1, j, rows, cols) && visit[i-1][j] == 0 && matrix[i-1][j] > matrix[i][j]){
+           int d =  (DP[i-1][j] == -1)? DFS(matrix, i-1, j, depth+1, DP, visit, rows, cols): depth+DP[i-1][j];
+           maxDepth = max(maxDepth, d);
+        }
+        if(insideBounds(i, j-1, rows, cols) && visit[i][j-1] == 0 && matrix[i][j-1] > matrix[i][j]){
+           int d =  (DP[i][j-1] == -1)? DFS(matrix, i, j-1, depth+1, DP, visit, rows, cols): depth+DP[i][j-1];
+           maxDepth = max(maxDepth, d);
+        }
+
+        visit[i][j] = 0;
+        DP[i][j] = max(maxDepth, depth) - depth + 1;
+        return max(maxDepth, depth);
+    }
+
+    int longestIncreasingPath(vvi& matrix) {
+        int rows = matrix.size();
+        if(rows == 0) return 0;
+        int cols = matrix[0].size();
+
+        vvi DP (rows, vector<int> (cols, -1));
+        vvi visit  (rows, vector<int> (cols, 0));
+        int maxLen = -1;
+        for(int i = 0; i < rows; i++){
+            for(int j = 0; j < cols; j++){
+                if(DP[i][j] == -1){
+                    DP[i][j] = DFS(matrix, i, j, 1, DP, visit, rows, cols);
+                }
+
+                if(DP[i][j] > maxLen) maxLen = DP[i][j];
+            }
+        }
+
+        return maxLen;
+    }
+};