UVa : 785 :: Grid Colouring

Problem : Please find the problem here.

Explanation : Just need to traverse the graph, could be solved by DFS or BFS. Input parsing is troublesome though. Good for practice.  

Code : Used DFS.

#include <bits/stdc++.h>
using namespace std;

const int mxN = 32, di[4]={1, 0, -1, 0}, dj[4]={0, 1, 0, -1};
int n, m;
string s[mxN], in, br;
char contour;

bool isok(int i, int j){
    return i>=0 && i<n && j>=0 && j<(int)s[i].length() && s[i][j] == ' ';
}

void dfs(int i, int j, char c){
    s[i][j] = c;
    for(int k = 0; k < 4; k++){
        int ni = i+di[k], nj = j+dj[k];
	if(s[ni][nj] != c && isok(ni, nj)){ 
	    dfs(ni, nj, c);
	}
    }
}

int main()
{
    ofstream fout("out");
    while(getline(cin, in)){
	int i = 0;
	do{
	    if(in[0] == '_'){
	        br = in;
	        break;
	    }
	    s[i] = in;

	    // lazy way to find contour,
	    if(i == 0){
		for(int j = 1; j < (int)in.length(); j++){
		    if(in[j]!=' ' && in[j]!='_' && in[j]==in[j-1]){
			contour = in[j];
			break;
		    }
		}
	    }
	    // ends here
	    i++;
	}while(getline(cin, in));
	

        n = i;

        // now look for marker and apply dfs from that point.
	for(int i = 0; i < n; i++){
	    for(int j = 0; j < (int)s[i].length(); j++){
		if(s[i][j] != contour && s[i][j] != ' ' && s[i][j] != '\t'){
		    dfs(i, j, s[i][j]);
		}
	    }
	}

	// finally print the grid.
	for(int i = 0; i < n; i++){
	    cout << s[i] << '\n';
	}

	// dont forget the seperation line -> "_______"
	cout << br << '\n';
    }	
    return 0;
}