Merge pull request #489 from harshita9621/master

Backtracking Rat in a Maze

Author: smv1999

Backtracking/Backtracking-Rat in a Maze.cpp

@@ -0,0 +1,118 @@
+/* Rat In a Maze
+ ---------------------------------------------------------------------
+ 
+Problem: Given a maze(2D matrix) with obstacles, starting from (0,0) you have to
+reach (n-1, n-1). If you are currently on (x,y), you can move to (x+1,y) or (x,y+1).
+You can not move to the walls.
+Idea: Try all the possible paths to see if you can reach (n-1,n-1) 
+
+--------------------------------------------------------------------------------
+
+Input:
+----
+0 denotes wall, 1 denotes free path
+two numbers n, m
+Next n lines contain m numbers (0 or 1)
+
+Output:
+--------
+Print 1 if rat can reach (n-1,m-1)
+Print 0 if it can not reach (n-1,m-1)
+
+------------------------
+
+Test Case 1:
+
+Input:
+5 5
+1 0 1 0 1
+1 1 1 1 1
+0 1 0 1 0
+1 0 0 1 1
+1 1 1 0 1
+
+Output:
+
+1 0 0 0 0
+1 1 1 1 0
+0 0 0 1 0
+0 0 0 1 1
+0 0 0 0 1
+
+*/
+
+
+#include <iostream>
+using namespace std;
+
+bool isSafe(int **arr, int x, int y, int n){
+	if(x<n && y<n && arr[x][y] == 1){
+		return true;
+	}
+	return false;
+}
+
+bool ratinMaze(int **arr, int x, int y,int n, int** solArr){
+	
+	if((x== (n-1)) && (y== (n-1))){
+		solArr[x][y]=1;
+		return true;
+	}
+	
+	if(isSafe(arr,x,y,n)){
+		solArr[x][y]==1;
+		if(ratinMaze(arr,x+1,y,n,solArr)){
+			return true;
+		}
+		if(ratinMaze(arr,x,y+1,n,solArr)){
+			return true;
+			}
+			
+		solArr[x][y]=0; //backtracking
+		return false;	
+		}
+	return false;
+		
+}
+
+int main(){
+	
+	int n;
+	cin>>n;
+	
+	int** arr=new int*[n];
+	for(int i=0;i<n;i++){
+		arr[i]=new int[n];
+	}
+	
+	for(int i=0;i<n;i++){
+		for(int j=0;j<n;j++){
+			cin>>arr[i][j];	
+    	}
+	}
+	
+		int** solArr=new int*[n];
+	    for(int i=0;i<n;i++){
+		solArr[i]=new int[n];
+			for(int j=0;j<n;j++){
+				solArr[i][j]=0;
+	        }
+	
+		}
+	
+	if(ratinMaze(arr,0,0,n,solArr)){
+		for(int i=0;i<n;i++){
+			for(int j=0;j<n;j++){
+				cout<<solArr[i][j]<<" ";	
+			} cout<<endl;
+		}
+		
+	}
+	
+	
+	return 0;
+}
+
+/* Time Complexity: O(2n)
+Space Complexity: O(2n)
+*/