11.2.2. Один конь

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
struct horse
{
    int x;
    int y;
    vector< pair< int, int > > v;
};
int px[9] = { 0, 2, 2, 1, 1, -1, -1, -2, -2 };
int py[9] = { 0, 1, -1, 2, -2, 2, -2, 1, -1 };
queue<horse> q;
horse p1, p2;
bool mark[30][30];
vector< pair< int, int> > temp, ans;
int main()
{
    int i, j, n, m, b, c, d, x1, y1, x2, y2;
    cin >> n;
    cin >> y1 >> x1 >> y2 >> x2;
    mark[x1][y1] = true;
    temp.push_back(make_pair(x1, y1));
    p1.x = x1;
    p1.y = y1;
    p1.v = temp;
    q.push(p1);
    while (!q.empty())
    {
        p1 = q.front();
        q.pop();
        if (p1.x == x2 && p1.y == y2)
        {
            ans = p1.v;
            break;
        }
        for (i = 1; i <= 8; ++i)
        {
            int x = p1.x + px[i];
            int y = p1.y + py[i];
            if (x>0 && y>0 && x <= n && y <= n && mark[x][y] == false)
            {
                mark[x][y] = true;
                temp = p1.v;
                temp.push_back(make_pair(x, y));
                p2.x = x;
                p2.y = y;
                p2.v = temp;
                q.push(p2);
            }
        }
    }
    cout << ans.size() - 1 << endl;
    for (i = 0; i<ans.size(); ++i)
        cout << ans[i].second << " " << ans[i].first << endl;
    return 0;

}