Table of contents

• Problem
• Solution

# Problem

http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_13_A

# Solution

// C++ 14
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
#include <math.h>

#define ll long long
#define Int int
#define loop(x, start, end) for(Int x = start; x < end; x++)
#define loopdown(x, start, end) for(int x = start; x > end; x--)
#define rep(n) for(int x = 0; x < n; x++)
#define span(a,x,y) a.begin()+x,a.begin()+y
#define span_all(a) a.begin(),a.end()
#define len(x) (x.size())
#define last(x) (*(x.end()-1))

using namespace std;

#define MAX_K 
#define W 8
Int K;
bool B[W][W];

#define FREE -1
#define NOT_FREE 1

vector<Int> rows(W, FREE), cols(W, FREE), dpos(W*2-1, FREE), dneg(W*2-1, FREE);

void input() {
  Int r, c;
  cin >> K;

  loop(r,0,W) {
    loop(c,0,W) {
      B[r][c] = false;
    }
  }

  loop(k,0,K) {
    cin >> r >> c;
    B[r][c] = true;
  }
}

void dump() {
  // Filter the answer
  loop(c,0,W) {
    loop(r,0,W) {
      if (B[r][c]) {
        if (rows[c] != r) return;
      }
    }
  }

  loop(c,0,W) {
    loop(r,0,W) {
      if (rows[r] == c) cout << 'Q';
      else cout << '.';
    }
    cout << endl;
  }
}

bool is_free(Int col, Int row) {
  return cols[row] == FREE && dpos[col + row] == FREE && dneg[col - row + W - 1] == FREE;
}

void rec(Int col) {
  if (col == W) {
    dump(); return;
  }

  loop(row,0,W) {
    if (!is_free(col, row)) continue;
    rows[col] = row;
    cols[row] = dpos[col + row] = dneg[col - row + W - 1] = NOT_FREE;

    rec(col + 1);

    rows[col] = cols[row] = dpos[col + row] = dneg[col - row + W - 1] = FREE;
  }
}

void solve() {
  rec(0);
}

int main(void) {
  input();
  solve();
}