AtCoder Beginning Contest 128

Posted 2021-12-07 jhseng

打完心情巨差，题目其实很简单，OJ垃圾。以后坚决不在这破OJ上用STL。

---

A：

一眼秒杀。

 1 /* basic header */
 2 #include <bits/stdc++.h>
 3 /* define */
 4 #define ll long long
 5 #define dou double
 6 #define pb emplace_back
 7 #define mp make_pair
 8 #define sot(a,b) sort(a+1,a+1+b)
 9 #define rep1(i,a,b) for(int i=a;i<=b;++i)
10 #define rep0(i,a,b) for(int i=a;i<b;++i)
11 #define eps 1e-8
12 #define int_inf 0x3f3f3f3f
13 #define ll_inf 0x7f7f7f7f7f7f7f7f
14 #define lson curPos<<1
15 #define rson curPos<<1|1
16 /* namespace */
17 using namespace std;
18 /* header end */
19 
20 int a, p;
21 
22 int main() {
23     cin >> a >> p;
24     cout << (a * 3 + p) / 2 << endl;
25     return 0;
26 }

View Code

B：

一眼秒杀。

 1 /* basic header */
 2 #include <bits/stdc++.h>
 3 /* define */
 4 #define ll long long
 5 #define dou double
 6 #define pb emplace_back
 7 #define mp make_pair
 8 #define sot(a,b) sort(a+1,a+1+b)
 9 #define rep1(i,a,b) for(int i=a;i<=b;++i)
10 #define rep0(i,a,b) for(int i=a;i<b;++i)
11 #define eps 1e-8
12 #define int_inf 0x3f3f3f3f
13 #define ll_inf 0x7f7f7f7f7f7f7f7f
14 #define lson curPos<<1
15 #define rson curPos<<1|1
16 /* namespace */
17 using namespace std;
18 /* header end */
19 
20 struct Node {
21     string s;
22     int score, pos;
23     Node() {}
24     Node(string a, int b, int c) {
25         s = a; score = b; pos = c;
26     }
27     bool operator<(const Node &rhs)const {
28         if (s != rhs.s) return s < rhs.s;
29         else return score > rhs.score;
30     }
31 };
32 
33 vector<Node>v;
34 
35 int main() {
36     int n; cin >> n;
37     rep1(i, 1, n) {
38         string s; int p; cin >> s >> p;
39         v.pb(s, p, i);
40     }
41     sort(v.begin(), v.end());
42     for (auto i : v) cout << i.pos << endl;
43     return 0;
44 }

View Code

C：

一眼秒杀，枚举所有开关状态即可。但是用set T了超久都没发现导致极度自闭，比赛结束前十分钟重构改成数组就A了。垃圾OJ。

 1 /* basic header */
 2 #include <bits/stdc++.h>
 3 /* define */
 4 #define ll long long
 5 #define dou double
 6 #define pb emplace_back
 7 #define mp make_pair
 8 #define sot(a,b) sort(a+1,a+1+b)
 9 #define rep1(i,a,b) for(int i=a;i<=b;++i)
10 #define rep0(i,a,b) for(int i=a;i<b;++i)
11 #define eps 1e-8
12 #define int_inf 0x3f3f3f3f
13 #define ll_inf 0x7f7f7f7f7f7f7f7f
14 #define lson curPos<<1
15 #define rson curPos<<1|1
16 /* namespace */
17 using namespace std;
18 /* header end */
19  
20 const int maxn = 15;
21 int n, m, p[maxn], ans = 0;
22 set<int>a[maxn]; //每个开关管哪些灯
23  
24 int main() {
25     cin >> n >> m;
26     rep1(i, 1, m) {
27         int k; cin >> k;
28         while (k--) {
29             int x; cin >> x;
30             a[x].insert(i);
31         }
32     }
33     rep1(i, 1, m) cin >> p[i];
34     int lim = pow(2, n);
35     int swit[maxn], time[maxn];
36     for (int i = 0; i < lim; i++) {
37         int tmp = i, cnt = m, flag = 1;
38         for (int j = 0; j < maxn; j++) swit[j] = time[j] = 0;
39         while (tmp) swit[cnt--] = tmp % 2, tmp >>= 1;
40         for (int j = 1; j <= m; j++)
41             if (swit[j])
42                 for (auto p : a[j]) time[p]++;
43         for (int j = 1; j <= m; j++)
44             if (time[j] % 2 != p[j]) {
45                 flag = 0; break;
46             }
47         if (flag) ans++;
48     }
49     cout << ans << endl;
50     return 0;
51 }

TLE Code

 1 /* basic header */
 2 #include <bits/stdc++.h>
 3 /* define */
 4 #define ll long long
 5 #define dou double
 6 #define pb emplace_back
 7 #define mp make_pair
 8 #define sot(a,b) sort(a+1,a+1+b)
 9 #define rep1(i,a,b) for(int i=a;i<=b;++i)
10 #define rep0(i,a,b) for(int i=a;i<b;++i)
11 #define eps 1e-8
12 #define int_inf 0x3f3f3f3f
13 #define ll_inf 0x7f7f7f7f7f7f7f7f
14 #define lson curPos<<1
15 #define rson curPos<<1|1
16 /* namespace */
17 using namespace std;
18 /* header end */
19 
20 const int maxn = 15;
21 int n, m, p[maxn], ans = 0, a[maxn][maxn];
22 
23 int main() {
24     scanf("%d%d", &n, &m);
25     rep1(i, 1, m) {
26         scanf("%d", &a[i][0]);
27         rep1(j, 1, a[i][0]) scanf("%d", &a[i][j]);
28     }
29     rep1(i, 1, m) scanf("%d", &p[i]);
30     rep1(i, 0, (1 << n) - 1) {
31         int flag = 1, cmp = i, swit[20], light[20], cnt = 0;
32         rep1(i, 1, 20) swit[i] = light[i] = 0;
33         while (cmp) swit[++cnt] = cmp & 1, cmp >>= 1;
34         rep1(i, 1, m)
35         rep1(j, 1, a[i][0]) light[i] += swit[a[i][j]];
36         rep1(i, 1, m) if ((light[i] % 2) != p[i]) {
37             flag = 0; break;
38         }
39         if (flag) ans++;
40     }
41     printf("%d\n", ans);
42     return 0;
43 }

AC Code

D：

一眼觉得是贪心，但是被上一题TLE搞到没心情想了。队友直接用了个O(n^3)的暴力枚举AC。先枚举答案由多少个数组成，再枚举从左边选的数的个数，最后枚举从右边选的数的个数。

正解也是枚举，但是如果这题数据量变大，能不能贪心呢？不太确定。

Code via. BWKPlus

 1 /* basic header */
 2 #include <bits/stdc++.h>
 3 /* define */
 4 #define ll long long
 5 #define dou double
 6 #define pb emplace_back
 7 #define mp make_pair
 8 #define sot(a,b) sort(a+1,a+1+b)
 9 #define rep1(i,a,b) for(int i=a;i<=b;++i)
10 #define rep0(i,a,b) for(int i=a;i<b;++i)
11 #define eps 1e-8
12 #define int_inf 0x3f3f3f3f
13 #define ll_inf 0x7f7f7f7f7f7f7f7f
14 #define lson curPos<<1
15 #define rson curPos<<1|1
16 /* namespace */
17 using namespace std;
18 /* header end */
19 
20 const int maxn = 60;
21 int a[maxn], now[maxn], ans = 0, n, m;
22 
23 int main() {
24     scanf("%d%d", &n, &m);
25     rep1(i, 1, n) scanf("%d", &a[i]);
26     for (int i = 1; i <= min(n, m); i++) {
27         rep1(j, 0, i) {
28             rep1(k, 0, n) now[k] = 0;
29             int cnt = 0;
30             rep1(k, 1, i - j) now[++cnt] = a[k];
31             rep1(k, 1, j) now[++cnt] = a[n - k + 1];
32             sot(now, i);
33             int tot = m - i, sum = 0, x = 1;
34             while (tot && now[x] < 0) x++, tot--;
35             for (; x <= i; x++) sum += now[x];
36             ans = max(ans, sum);
37         }
38     }
39     printf("%d\n", ans);
40     return 0;
41 }

View Code

E&&F：

待补。