【HDOJ】2717 Catch That Cow

bfs。

 /* 2717 */
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <queue>
 using namespace std;

 #define MAXN 100001

 queue<int> Q;
 int s[MAXN];
 int n, k;
 int ans;

 void bfs() {
     int cur, nxt;

     while (!Q.empty())
         Q.pop();

     memset(s, , sizeof(s));

     Q.push(n);
     while (!Q.empty()) {
         cur = Q.front();
         Q.pop();
         if (cur == k)
             break;
         nxt = cur - ;
         if (nxt>= && s[nxt]==) {
             Q.push(nxt);
             s[nxt] = s[cur] + ;
         }
         nxt = cur + ;
         if (nxt<MAXN && s[nxt]==) {
             Q.push(nxt);
             s[nxt] = s[cur] + ;
         }
         nxt = cur + cur;
         if (nxt<MAXN && (nxt-k)<(k-cur) && s[nxt]==) {
             Q.push(nxt);
             s[nxt] = s[cur] + ;
         }
     }
 }

 int main() {

 #ifndef ONLINE_JUDGE
     freopen("data.in", "r", stdin);
 #endif

     while (scanf("%d %d", &n, &k) != EOF) {
         if (n >= k)
             printf("%d\n", n-k);
         else {
             bfs();
             printf("%d\n", s[k]);
         }
     }

     return ;
 }