Catch That Cow

POJ - 3278

BFS很簡單，有三種方向，按BFS板子走一遍就行了

//#include <bits/stdc++.h>
#include <cstring>
#include <iostream>
#include <set>
#include <queue>
#include <stack>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;

int mod = 9973;
const int INF = 0x3f3f3f3;
const int maxn = 1e5 + 10;
int vis[maxn];//檢測是否來過，來過了再走一遍就沒意義了
int n, k;
struct node
{
	int step;
	int x;
};//這道題要記錄步數，所以用結構體

int main()
{
	cin >> n >> k;
	if (k <= n)
	{
		cout << n - k;//後退只有一種方法
		return 0;
	}
	queue<node> q;
	node tem;
	tem.step = 0;
	tem.x = n;
	q.push(tem);
	vis[n] = 1;
	while (!q.empty())
	{
		node t = q.front();
		q.pop();
		node t1, t2, t3;
		t1.step = t2.step = t3.step = t.step + 1;
		t1.x = t.x - 1, t2.x = t.x + 1, t3.x = t.x * 2;
		if (t1.x == k || t2.x == k || t3.x == k)
		{
			cout << t1.step;
			return 0;
		}
		if (t1.x >= 0 && (!vis[t1.x]))
		{
			q.push(t1);
			vis[t1.x] = 1;
		}
		if (!vis[t2.x])
		{
			q.push(t2);
			vis[t2.x] = 1;
		}
		if (t3.x < maxn && (!vis[t3.x]))
		{
			q.push(t3);
			vis[t3.x] = 1;
		}
	}
	return 0;
}