棋盘覆盖

int tile = 0;
void ChessBoard(int tr, int tc, int dr, int dc, int size) {
    if (size == 1) {
        return;
    }
    int t = tile++;
    s = size / 2;
    if (dr < tr + s && dc < tc + s) {
        ChessBoard(tr, tc, dr, dc, s);
    } else {
        board[tr + s - 1][tc + s - 1] = t;
        ChessBoard(tr, tc, tr + s - 1, tc + s - 1, s);
    }
    if (dr < tr + s && dc >= tc + s) {
        ChessBoard(tr, tc + s, dr, dc, s);
    } else {
        board[tr + s - 1][tc + s] = t;
        ChessBoard(tr, tc + s, tr + s - 1, tc + s, s);
    }
    if (dr >= tr + s && dc < tc + s) {
        ChessBoard(tr + s, tc, dr, dc, s);
    } else {
        board[tr + s][tc + s - 1] = t;
        ChessBoard(tr + s, tc, tr + s, tc + s - 1, s);
    }
    if (dr >= tr + s && dc >= tc + s) {
        ChessBoard(tr + s, tc + s, dr, dc, s);
    } else {
        board[tr + s][tc + s] = t;
        ChessBoard(tr + s, tc + s, tr + s, tc + s, s);
    }
}