牛客练习赛16

Posted 2020-11-01 Algorithms Crush Me

A.字典序最大的子序列

倒着贪心

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 char s[111111];
 4  
 5 int main(){
 6     string ans = "";
 7     scanf("%s", s + 1);
 8     int len = strlen(s + 1);
 9     ans += s[len];
10     for(int i = len - 1; i >= 1; i--){
11         if(s[i] >= ans[ans.length()-1]) ans += s[i];
12     }
13     reverse(ans.begin(), ans.end());
14     cout << ans << endl;
15     return 0;
16 }

Aguin

 

B.漂亮的树

减个等差

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 1e5;
 4 int a[maxn];
 5 map<int, int> cnt;
 6 map<int, int> :: iterator it;
 7  
 8 int main(){
 9     int n;
10     scanf("%d", &n);
11     for(int i = 1; i <= n; ++i) scanf("%d", a + i);
12     for(int i = 1; i <= n / 2; ++i){
13         a[i] -= i;
14         a[n-i+1] -= i;
15         cnt[a[i]]++;
16         cnt[a[n-i+1]]++;
17     }
18     if(n % 2) a[n/2+1] -= n/2+1, cnt[a[n/2+1]]++;
19     int ans = n;
20     for(it = cnt.begin(); it != cnt.end(); it++){
21         ans = min(ans, n - (*it).second);
22     }
23     cout << ans << endl;
24     return 0;
25 }

Aguin

 

C.任意点

数连通块

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int fa[111];
 4 int Find(int x){
 5     return fa[x] == x ? x : fa[x] = Find(fa[x]);
 6 }
 7 void Union(int x, int y){
 8     x = Find(x), y = Find(y);
 9     fa[x] = y;
10 }
11 int xx[111], yy[111];
12 int main(){
13     int n, ans = -1;
14     scanf("%d", &n);
15     for(int i = 1; i <= n; ++i){
16         fa[i] = i;
17         scanf("%d %d", xx + i, yy + i);
18         for(int j = 1; j < i; ++j)
19             if(xx[i] == xx[j] || yy[i] == yy[j]) Union(i, j);
20     }
21     for(int i = 1; i <= n; ++i){
22         if(fa[i] == i) ans++;
23     }
24     printf("%d\n", ans);
25     return 0;
26 }

Aguin

 

D.k进制数

模k-1不变

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 const int maxn = 1e5 + 10;
 5 LL a[maxn], sum[maxn];
 6 map<LL, LL> cnt;
 7  
 8 int main(){
 9     LL k, b, n, ans = 0, t = 0, z = 0;
10     scanf("%lld %lld %lld", &k, &b, &n);
11     for(int i = 1; i <= n; ++i){
12         scanf("%lld", a + i);
13         sum[i] = (sum[i-1] + a[i]) % (k - 1);
14         if(a[i] == 0) t++, z += t;
15         else t = 0;
16     }
17     if(b == 0) ans = z;
18     else {
19         cnt[0]++;
20         for(int i = 1; i <= n; ++i)
21             ans += cnt[(sum[i]-b+k-1)%(k-1)], cnt[sum[i]]++;
22         if(b == k - 1) ans -= z;
23     }
24     printf("%lld\n", ans);
25     return 0;
26 }

Aguin

 

E.求值

找变化点

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 const int maxn = 1e5 + 10;
 5 LL a[maxn];
 6 set<int> pos, v;
 7 set<int> :: reverse_iterator it;
 8  
 9 int main(){
10     int n;
11     scanf("%d", &n);
12     for(int i = 1; i <= n; ++i){
13         scanf("%d", a + i);
14         v.insert(a[i]);
15         int tmp = a[i];
16         vector<int> cl;
17         for(it = pos.rbegin(); it != pos.rend(); it++){
18             if((a[*it] | tmp) != tmp) tmp |= a[*it], v.insert(tmp);
19             else cl.push_back(*it);
20         }
21         for(int j = 0; j < cl.size(); j++) pos.erase(cl[j]);
22         pos.insert(i);
23     }
24     printf("%d\n", v.size());
25     return 0;
26 }

Aguin

 

F.选值

随便加加

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 const int maxn = 1e5 + 10;
 5 LL a[maxn];
 6  
 7 int main(){
 8     int n;
 9     LL d, ans = 0;
10     scanf("%d %lld", &n, &d);
11     for(int i = 1; i <= n; ++i){
12         scanf("%lld", a + i);
13         int j = lower_bound(a + 1, a + 1 + i, a[i] - d) - a;
14         ans += (i - j) * (LL)(i - j - 1) / 2;
15     }
16     cout << ans << endl;
17     return 0;
18 }

Aguin