In the solution to the problem The Great Revegetation why do we do if (B[j] == i && G[A[j]] == g) ok = false; instead of if ((a[j] == i || b[j] == i) && grass[a[j]] == color)?
#include <iostream>
#include <fstream>
using namespace std;
int main(void)
{
int N, M;
int A[151], B[151], G[101];
ifstream fin ("revegetate.in");
fin >> N >> M;
for (int i=0; i<M; i++) {
fin >> A[i] >> B[i];
if (A[i] > B[i]) swap (A[i], B[i]);
}
ofstream fout ("revegetate.out");
for (int i=1; i<=N; i++) {
int g;
for (g = 1; g <= 4; g++) {
bool ok = true;
for (int j=0; j<M; j++)
if (B[j] == i && G[A[j]] == g) ok = false; // <-- I am talking about this line
if (ok) break;
}
G[i] = g;
fout << g;
}
fout << "\n";
return 0;
}