I am a beginner in java. I have been working on an maze problem trying it solve it by recursion. I have written the code which seems to work on few inputs and not others. The input is a maze consisting of 0's and 1's. # is the start and @ is the exit.0 is wall and 1's are open.The output will be the hops from # to @. Though i am solving the problem by recursion,I must be going wrong with the logic. Please let me know where I am wrong.
Class practisenumwords
import java.util.Scanner;
class practisenumwords {
public static void main(String[] args){
Scanner in=new Scanner(System.in);
int r=in.nextInt();
int c=in.nextInt();
maze maz=new maze(r,c); /*input in string copied to array*/
char[] ch;
ch = "00000000111111101111011001101@#11100".toCharArray();
int l=0;
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++) /*initialising the maze elements*/
{
maz.m[i][j]=new cells();
maz.m[i][j].c=ch[l];
maz.m[i][j].row=i;
maz.m[i][j].col=j;
l++;
}
}
for(int i=0;i<r;i++) /*print the input maze */
{
for(int j=0;j<c;j++)
{
System.out.print(""+maz.m[i][j].c);
}
System.out.println();
}
maz.escape();
maz.find(maz.startx,maz.starty,maz.hops);
}
}
Class cells
class cells {
char c;
int row;
int col;
boolean done=false; /*initially all cells are unvisited*/
}
Class maze
class maze{
maze (int a,int b){
rows=a;
cols=b;
m=new cells[rows][cols];
}
int rows;
int cols;
cells[][] m;
int startx,starty;
int hops=0;
void escape()
{
for(int i=0;i<rows;i++)
{
for(int j=0;j<cols;j++)
{
if(m[i][j].c=='#')
{
startx=i;
starty=j;
System.out.println(startx+" "+starty);
}
}
}
}
void find(int x,int y,int h)
{
if ((x+1<rows && m[x+1][y].c=='@' && m[x+1][y].done!=true)
||(x-1>=0 && m[x-1][y].c=='@' && m[x-1][y].done!=true)
||(y+1<cols && m[x][y+1].c=='@' && m[x][y+1].done!=true)
||(y-1>=0 && m[x][y-1].c=='@' && m[x][y-1].done!=true)){
h++;
System.out.println(h);
}
else
{
if(x-1>=0 && m[x-1][y].c=='1' && m[x-1][y].done!=true){ /*north cell*/
m[x][y].done=true;
h++;
find(x-1,y,h);
}
if(x+1<rows && m[x+1][y].c=='1' && m[x+1][y].done!=true){ /*south cell*/
m[x][y].done=true;
h++;
find(x+1,y,h);
}
if(y+1<cols && m[x][y+1].c=='1' && m[x][y+1].done!=true){ /*east cell*/
m[x][y].done=true;
h++;
find(x,y+1,h);
}
if(y-1>=0 && m[x][y-1].c=='1' && m[x][y-1].done!=true){ /*west cell*/
m[x][y].done=true;
h++;
find(x,y-1,h);
}
}
}
}
Now,i get the right output for the inputs as the 1 in program.
000000
001111
111011
110110
01101@
#11100
output- 12 (obtaining right output)
00@000
001111
111011
110110
011011
#11100
output- 7 (obtaining right output)
BUT NOT FOR OTHER INPUTS like
0 0 0 0 @ 0
0 1 0 1 1 0
1 1 1 1 0 1
0 1 0 1 0 0
0 0 # 1 1 1
0 1 1 0 0 1
correct output - 6 output obtained -7
Also the output changes with the order in which the adjacent cells are checked.
Honestly, I'd implement your recursive function a little differently:
And there's no need to check whether a bool value is != true
, !boolValue
is fine.
int find(int x,int y,int h)
{
int result = -1;
if ((x+1<rows && m[x+1][y].c=='@' && !m[x+1][y].done)
||(x-1>=0 && m[x-1][y].c=='@' && !m[x-1][y].done)
||(y+1<cols && m[x][y+1].c=='@' && !m[x][y+1].done)
||(y-1>=0 && m[x][y-1].c=='@' && !m[x][y-1].done)){
return h + 1;
}
else
{
if(x-1>=0 && m[x-1][y].c=='1' && !m[x-1][y].done){ /*north cell*/
m[x][y].done=true;
result = find(x-1,y,h + 1)
if (result > -1) {
return result;
}
m[x][y].done=false;
}
Implement the other three directions the same way, then result should still be -1 if no solution was found.
return result;
}
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