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  1. #include<bits/stdc++.h>
  2. #define PB push_back
  3. #define endl '\n';
  4. using ll = long long;
  5. using namespace std;
  6. const int maxN = 1e6;
  7. const int MOD = 1e9 + 7;
  8. int dx4[4] = {-1, 0, 0, 1};
  9. int dy4[4] = {0, -1, 1, 0};
  10. int dx8[8] = {-1, -1, -1, 0, 0, 1, 1, 1};
  11. int dy8[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
  12. vector<bool> visited(maxN, false);
  13. vector<int> adj[maxN];
  14. vector<int> parent(maxN, 0);
  15. int n, m;
  16. int bfs(int n, int m){
  17. 	if(n >= m){
  18. 		return n - m;
  19. 	}
  20. 	queue<pair<int, int>> q;
  21. 	q.push(make_pair(n, 0));
  22. 	set<int> s;
  23. 	s.insert(n);
  24. 	while(!q.empty()){
  25. 		int x = q.front().first;
  26. 		int y = q.front().second;
  27. 		q.pop();
  28. 		if(x == m){
  29. 			return y;
  30. 		}
  31. 		if(s.find(x*2) == s.end()){
  32. 			q.push(make_pair(x*2, y + 1));
  33. 			s.insert(x*2);
  34. 		}
  35. 		if(x - 1 >= 0 && s.find(x - 1) == s.end()){
  36. 			q.push(make_pair(x - 1, y + 1));
  37. 			s.insert(x - 1); 
  38. 		} 
  39. 	}
  40. 	return -1;
  41. }
  42. int main() {
  43.     ios_base::sync_with_stdio(0);
  44.     cin.tie(nullptr);
  45.     cout.tie(0);
  46.     cin >> n >> m;
  47.     cout << bfs(n, m);
  48.     return 0;
  49. }
Success #stdin #stdout 0.01s 30500KB
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https://ideone.com/GEObVE
language:
C++14 (gcc 8.3)
created:
6 days ago
visibility:
public

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