Java广度优先搜索

package graph.poj3278;
 
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
 
public class POJ3278BFS {
    static final int MAXN = 100009;
    static boolean vis[] = new boolean[MAXN];
    static int d[] = new int[MAXN];
    static int n, k;
 
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        n = scanner.nextInt();
        k = scanner.nextInt();
 
        if (k <= n) {
            System.out.println(n - k);
            return;
        }
        solve();
    }
 
    static void solve() {
        Queue<Integer> q = new LinkedList<>();
        vis[n] = true;
        d[n] = 0;
        q.add(n);
        while (!q.isEmpty()) {
            int u = q.peek();
            q.poll();
            if (u == k) {
                System.out.println(d[k]);
                return;
            }
            int x;
            x = u + 1;
            if (x >= 0 && x <= 100000 && !vis[x]) { // 向前走一步
                d[x] = d[u] + 1;
                vis[x] = true;
                q.add(x);
            }
            x = u - 1;
            if (x >= 0 && x <= 100000 && !vis[x]) { // 向后走一步
                d[x] = d[u] + 1;
                vis[x] = true;
                q.add(x);
            }
            x = u * 2;
            if (x >= 0 && x <= 100000 && !vis[x]) { // 跳着走
                d[x] = d[u] + 1;
                vis[x] = true;
                q.add(x);
            }
        }
    }
}