Here you will find solutions of many problems on spoj. If you want solution of some problem which is not listed in blog or have doubt regarding any spoj problem (which i have solved) or any programming concept (data structure) you can mail me @ raj.nishant360@gmail.com
And my humble request to you all that don't copy the code only try to understand the logic and algorithm behind the code. I have started this because if you tried as hard as you can and still can't find any solution to the problem then you can refer to this.
You can read my answer how to start competitive programming CLICK HERE

Monday, August 17, 2015

COMCB-Complete Chess Boards

Complete Chess Boards

Given below c++11 code is for COMCB spoj or Complete Chess Boards spoj.

Hint :- dfs with backtracking ,
for each node apply DFS and check if traversal of chess board is possible or not . Inside send child node in lexicographical order so that final path will be lexicographically shortest.


/*
===================================================
Name :- Nishant Raj
Email :- raj.nishant360@gmail.com
College :- Indian School of Mines
Branch :- Computer Science and Engineering
Time :- 17 August 2015 (Monday) 04:58
===================================================*/
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair < int , int >
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define mod 1000000009
int x[8] = {-1,1,-2,2,-2,2,-1,1};
int y[8] = {-2,-2,-1,-1,1,1,2,2};
int n , m;
bool valid(int row , int col){
    if(row>=0 && row< n && col >=0 && col < m)
        return true;
    return false;
}
bool dfs(vector<string> path ,int row ,int col , int count, int check[][30]){
    string temp = "";
    char c = (char)(col + 65);
    temp.pb(c);
    temp.append(to_string(row+1));
    path.pb(temp);
    if(count == m*n){
        for(int i = 0 ; i < path.size() ; i++)
            cout<<path[i];
        cout<<endl;
        return true;
    }
    int p , q;
    for(int i = 0 ; i < 8 ; i++){
        p = row + x[i] , q = col + y[i];
        if(valid(p , q) && !check[p][q]){
            check[p][q] = 1;
            if(dfs( path , p , q , count+1 , check)) return true;
            check[p][q] = 0;
        }
    }
    return false;
}
bool path(){
    for(int i = 0 ; i < n; i ++){
        for(int j = 0 ; j < m ; j++){
            int check[30][30];
            memset(check , 0 , sizeof check);
            check[i][j] = 1;
            vector<string> path;
            if(dfs(path , i , j ,1 , check )) return true;
        }
    }
    return false;
}
int main(){ 
     
    int t;
    cin>>t;
    while(t--){
        cin>>n>>m;
        if(!path()) cout<<-1<<endl;
    }
    
    return 0;
}