Create 11_uniquePathsiii.cpp

11 November Leetcode Challenge 2021/11_uniquePathsiii.cpp

@@ -0,0 +1,63 @@
+static int X[4] = {-1, 0, 1, 0};
+static int Y[4] = {0, -1, 0, 1};
+
+class Solution {
+public:
+
+    int countPaths(vector<vector<int>>& grid, int x, int y, int empty, const int& m, const int& n) {
+
+		/*
+		for(int i=0; i<m; i++) {
+			for(int j=0; j<n; j++) {
+				cout << grid[i][j] << " ";
+			}
+			cout << endl;
+		}
+		cout << x << " : " << y << " -> " << empty << endl << endl;
+		*/
+
+		// If we reach end cell and 
+		// All empty cells are visited, then return 1
+		// Else return 0
+        if(grid[x][y] == 2) {
+            return (empty == 0);
+        }
+
+        int count = 0;   // Count of possible paths from current cell {x,y}
+        grid[x][y] = -1;  // Visit
+
+		// Check for all valid directions
+        for(int k=0; k<4; k++) {
+			// Possible adjacent coordinates
+            int i = x + X[k];
+            int j = y + Y[k];
+
+			// Valid Moves
+            if(i>=0 && j>=0 && i<m && j<n && grid[i][j] != -1) {
+                count += countPaths(grid, i, j, empty-1, m, n);  // Add count of possible paths
+            }
+        }
+
+		// Backtrack 
+        grid[x][y] = 0;  // Unvisit
+
+        return count;
+    }
+
+    int uniquePathsIII(vector<vector<int>>& grid) {
+
+        int m = grid.size(), n = grid[0].size(), empty = 1;
+
+        pair<int, int> start;
+
+        for(int i=0; i<m; i++) {
+            for(int j=0; j<n; j++) {
+                if(grid[i][j] == 1) start = {i, j};
+                else if(grid[i][j] == 0) empty++;  // Count of empty cells
+            }
+        }
+
+		// Explore grid from start cell
+        return countPaths(grid, start.first, start.second, empty, m, n);
+    }
+};