问题链接
http://poj.org/problem?id=3278
摘自王道笔试指南
#include <iostream>
#include <string>
#include <vector>
#include <queue>
using namespace std;
const int MAXN = 100001;
vector<bool> inq(MAXN, false);
struct Status
{
int loc;
int time;
Status() { }
Status(int _loc, int _time) : loc(_loc), time(_time) { }
};
int BFS(int n, int k) {
queue<Status> que;
que.push(Status(n, 0));
inq[n] = true;
while (!que.empty()) {
Status p = que.front();
que.pop();
if (p.loc == k) {
return p.time;
}
for (int i = 0; i < 3; i++) {
Status next;
if (i == 0) {
next.loc = p.loc - 1;
}
else if (i == 1) {
next.loc = p.loc + 1;
}
else {
next.loc = p.loc * 2;
}
next.time = p.time + 1;
if (next.loc < 0 || next.loc >= MAXN || inq[next.loc]) {
continue;
}
que.push(next);
inq[next.loc] = true;
}
}
return -1;
}
int main()
{
int n, k;
cin >> n >> k;
int t = BFS(n, k);
cout << t << endl;
return 0;
}