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Author: alteos98

Exhaustive search and generation/P38211.cc

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+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+vector<int> t; //les reines
+
+vector<int> mc; //marquem si hi ha reina a la columna mc[k]
+vector<int> md1; //marquem si hi ha reina a la diagonal 1, i + j = k, md1[k]
+vector<int> md2; //marquem si hi ha reina a la diagonal 2, n + i - j - 1 = k, md2[k]
+
+void escriu_tauler () {
+	for (int i=0; i < t.size(); ++i) {
+		for (int j=0; j < t.size(); ++j) {
+			if (t[i] == j) cout << "Q";
+			else cout << ".";
+		}
+		cout << endl;
+	}
+}
+
+int calcul_diagonal1 (int i, int j) {
+	return i + j;
+}
+
+int calcul_diagonal2 (int i, int j, int n) {
+	return n + i - j - 1;
+}
+
+int reines (int i, int n, bool& trobat) {
+	if (i == n) {
+		escriu_tauler();
+		trobat = true;
+	}
+	else {
+		int j = 0;
+		while (j < n and !trobat) {
+			if (mc[j] == 0 and md1[calcul_diagonal1(i,j)] == 0 and md2[calcul_diagonal2(i,j,n)] == 0) {
+				t[i] = j;
+				mc[j] = 1;
+				md1[calcul_diagonal1(i,j)] = 1;
+				md2[calcul_diagonal2(i,j,n)] = 1;
+				reines(i+1,n,trobat);
+				mc[j] = 0;
+				md1[calcul_diagonal1(i,j)] = 0;
+				md2[calcul_diagonal2(i,j,n)] = 0;
+			}
+			++j;
+		}
+	}
+}
+
+int main() {
+	int n;
+	cin >> n;
+	t = vector<int> (n, -1);
+	mc = vector<int> (n, 0);
+	md1 = vector<int> (2*n-1, 0);
+	md2 = vector<int> (2*n-1, 0);
+	bool trobat = false;
+	reines(0,n,trobat);
+	if (not trobat) cout << "NO SOLUTION" << endl;
+}