## Problem Info

Chessboard and Queens to problem here

## My Work

```
#include <bits/stdc++.h>
using namespace std;
char tab[8][8];
int ans = 0;
bool isValid(int current , int tosee){
if(tab[current][tosee]=='*')
{
return false;
}
for(int i = 0 ; i < current ; i++)
{
if(tab[i][tosee]=='1')
{
return false;
}
}
for(int x = current , y = tosee ; x > 0 && y > 0 ; x-- , y--)
{
if(tab[x][y] == '1')
{
return false;
}
}
for(int x = current , y = tosee ; x > 0 && y > 0 ; x-- , y++)
{
if(tab[x][y] == '1')
{
return false;
}
}
return true;
}
void backtrack(int current_queen , int previous_pos){
if(current_queen >8 || current_queen < 0)
{
// if current queen is under or above 0 stop backtracking
if(current_queen > 8)
{
// one answer found
ans++;
return;
}
else
{
// no further possible answers
cout << ans;
exit(0);
}
}
else
{
for(int i = 0 ; i < 8 ; i++)
{
// for each position in the ligne check if its a valid placement ( recusively )
if(isValid(current_queen,i))
{
tab[current_queen][i]='1';
previous_pos = i;
backtrack(current_queen+1 , previous_pos);
}
}
// backtracking to find new solutions
tab[current_queen][previous_pos] = '.';
backtrack(current_queen-1 , previous_pos);
}
}
int main()
{
for(int i = 0 ; i < 8 ;i++)
for(int j = 0 ; j < 8 ;j++)
cin >> tab[i][j];
backtrack(0 , 0);
return 0;
}
```

classical backtracking through all possible positions to place the queen.

## What I’ve Tried

the logic that i am following is this :

- Start in the leftmost column
- If all queens are placed

return true - Try all rows in the current column.

Do following for every tried row.

a) If the queen can be placed safely in this row

then mark this [row, column] as part of the

solution and recursively check if placing

queen here leads to a solution.

b) If placing the queen in [row, column] leads to

a solution then return true.

c) If placing queen doesn’t lead to a solution then

unmark this [row, column] (Backtrack) and go to

step (a) to try other rows. - If all rows have been tried and nothing worked,

return false to trigger backtracking.

i think its my understading or implementation of backtracking that is off but i just can’t understand the tutorials on it …

## Question

please help me to see if my implementation is corret?