leetcode-go/poj/3278.catch-that-cow/main.cc

#include <cstdio>
#include <cstring>
#include <queue>

using namespace std;

const int L = 200001;

bool set[L];

int main() {
  int N, K;
  scanf("%d %d", &N, &K);
  queue<int> q;
  q.push(N);
  memset(set, 0, sizeof(set));
  set[N] = true;
  int s = 1, t = 0;
  while (s != 0) {
    int n = q.front();
    q.pop();
    s--;
    if (n == K) break;
    if (n < K) {
      if (!set[2 * n]) {
        q.push(2 * n);
        set[2 * n] = true;
      }
      if (!set[n + 1]) {
        q.push(n + 1);
        set[n + 1] = true;
      }
    }
    if (0 < n && !set[n - 1]) {
      q.push(n - 1);
      set[n - 1] = true;
    }
    if (s == 0) {
      s = q.size();
      t++;
    }
  }
  printf("%d\n", t);
  return 0;
}