Time Limit: 2000MS | Memory Limit: 65536KB | 64bit IO Format: %I64d & %I64u |
Description
Farmer John has been informed of the location of a fugitive cow and wants to catch her immediately. He starts at a point N (0 ≤ N ≤ 100,000) on a number line and the cow is at a point K(0 ≤ K ≤ 100,000) on the same number line. Farmer John has two modes of transportation: walking and teleporting.
* Walking: FJ can move from any point X to the points X – 1 or X + 1 in a single minute
* Teleporting: FJ can move from any point X to the point 2 × X in a single minute.
If the cow, unaware of its pursuit, does not move at all, how long does it take for Farmer John to retrieve it?
Input
Output
Sample Input
5 17
Sample Output
4
Hint
Source
#include <cstdio> #include <queue> using namespace std; queue <int> q; int n, k; int step[100010]; bool vis[100010]; void input() { scanf("%d%d", &n, &k); } inline bool check(int pos) { if (pos < 0 || pos > 100000 || vis[pos]) return 0; return 1; } void bfs() { q.push(n); while (!q.empty()) { int u = q.front(); q.pop(); if (u == k) { printf("%d\n", step[u]); return; } if (check(u + 1)) { step[u + 1] = step[u] + 1; vis[u + 1] = 1; q.push(u + 1); } if (check(u - 1)) { step[u - 1] = step[u] + 1; vis[u - 1] = 1; q.push(u - 1); } if (check(u * 2)) { step[u * 2] = step[u] + 1; vis[u * 2] = 1; q.push(u * 2); } } } int main() { input(); bfs(); return 0; }
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