Create ways_maze.cpp

dynamic_programming/ways_maze.cpp

@@ -0,0 +1,81 @@
+
+// C++ program to count number of paths in a maze 
+// with obstacles. 
+#include<bits/stdc++.h> 
+using namespace std; 
+#define R 4 
+#define C 4 
+
+// Returns count of possible paths in a maze[R][C] 
+// from (0,0) to (R-1,C-1) 
+int countPaths(int maze[][C]) 
+{ 
+    // If the initial cell is blocked, there is no 
+    // way of moving anywhere 
+    if (maze[0][0]==-1) 
+        return 0; 
+
+    // Initializing the leftmost column 
+    for (int i=0; i<R; i++) 
+    { 
+        if (maze[i][0] == 0) 
+            maze[i][0] = 1; 
+
+        // If we encounter a blocked cell in leftmost 
+        // row, there is no way of visiting any cell 
+        // directly below it. 
+        else
+            break; 
+    } 
+
+    // Similarly initialize the topmost row 
+    for (int i=1; i<C; i++) 
+    { 
+        if (maze[0][i] == 0) 
+            maze[0][i] = 1; 
+
+        // If we encounter a blocked cell in bottommost 
+        // row, there is no way of visiting any cell 
+        // directly below it. 
+        else
+            break; 
+    } 
+
+    // The only difference is that if a cell is -1, 
+    // simply ignore it else recursively compute 
+    // count value maze[i][j] 
+    for (int i=1; i<R; i++) 
+    { 
+        for (int j=1; j<C; j++) 
+        { 
+            // If blockage is found, ignore this cell  
+            if (maze[i][j] == -1) 
+                continue; 
+
+            // If we can reach maze[i][j] from maze[i-1][j] 
+            // then increment count. 
+            if (maze[i-1][j] > 0) 
+                maze[i][j] = (maze[i][j] + maze[i-1][j]); 
+
+            // If we can reach maze[i][j] from maze[i][j-1] 
+            // then increment count. 
+            if (maze[i][j-1] > 0) 
+                maze[i][j] = (maze[i][j] + maze[i][j-1]); 
+        } 
+    } 
+
+    // If the final cell is blocked, output 0, otherwise 
+    // the answer 
+    return (maze[R-1][C-1] > 0)? maze[R-1][C-1] : 0; 
+} 
+
+// Driver code 
+int main() 
+{ 
+    int maze[R][C] =  {{0,  0, 0, 0}, 
+                       {0, -1, 0, 0}, 
+                       {-1, 0, 0, 0}, 
+                       {0,  0, 0, 0}}; 
+    cout << countPaths(maze); 
+    return 0; 
+}