pat乙级每日习题

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 int main(int argc, char const *argv[])
 5 {
 6     int n;cin >> n;
 7     int ans = 0;
 8     while(n != 1){
 9         if((n & 1) == 1){
10             n = (n * 3 + 1) >> 1;
11         }else{
12             n >>= 1;
13         }
14         ++ans;
15     }
16     cout << ans << endl;
17     return 0;
18 }

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 const int N = 110;
 5 
 6 int arr[N];
 7 int n;
 8 
 9 int main(int argc, char const *argv[])
10 {
11     unordered_map<int, bool> hash;
12 
13     cin >> n;
14     for(int i = 1;i <= n;++i){
15         cin >> arr[i];//存进数组因为求答案要用
16         int x = arr[i];
17         //把x最终变成1的所有中间的数都置为true，代表出现过
18         while(x != 1){
19             if((x & 1) == 1) //&1 == 1 代表是奇数
20                 x = (3 * x + 1) >> 1;
21             else 
22                 x >>= 1;
23             hash[x] = true;
24         }
25     }
26 
27     vector<int> ans;
28     //把数组中的数没有被覆盖过的也就是 false 的加进答案
29     for(int i = 1;i <= n;++i)
30         if(!hash[arr[i]])
31             ans.push_back(arr[i]);    
32     //以下代码完全是为了格式化输出
33     sort(ans.begin(), ans.end(), greater<int>());
34     for(int i = 0;i < ans.size()-1;++i)
35         cout << ans[i] << " ";
36     cout << ans[ans.size()-1];
37     cout << endl;
38 
39     return 0;
40 }

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 const int N = 1e5;
 5 
 6 int n;
 7 bool state[N];
 8 
 9 int main(int argc, char const *argv[])
10 {
11     cin >> n;
12     int ans = 0;
13     int pre = -1;
14     for(int i = 2;i <= n;++i){
15         if(!state[i]){
16             if(i - pre == 2) 
17                 ++ans;
18             pre = i;
19             for(int j = i + i; j <= n; j += i)
20                 state[j] = true;
21         }
22     }
23     cout << ans << endl;
24     return 0;
25 }