题目链接：https://codeforces.com/contest/1303
A：
白给
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 = 110;
21 int t;
22 char s[maxn];
23
24 int main() {
25 scanf("%d", &t);
26 while (t--) {
27 int ans = 0;
28 scanf("%s", s + 1);
29 int len = strlen(s + 1);
30 int p, q;
31 for (p = 1; p <= len; p++)
32 if (s[p] == '1') break;
33 for (q = len; q >= 1; q--)
34 if (s[q] == '1') break;
35 for (int i = p; i <= q; i++)
36 if (s[i] == '0') ans++;
37 printf("%d\n", ans);
38 }
39 return 0;
40 }
B：
写了个傻逼做法，崩了
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 t;
21 // ll n, g, b;
22
23 // int main() {
24 // scanf("%d", &t);
25 // while (t--) {
26 // scanf("%lld%lld%lld", &n, &g, &b);
27 // ll goodNum = 0, badNum = 0, weekCount, ans = 0;
28 // goodNum = n & 1 ? n / 2 + 1 : n / 2; badNum = n - goodNum;
29 // weekCount = goodNum / g - 1;
30 // goodNum -= weekCount * g, badNum -= weekCount * b;
31 // if (goodNum < 0) goodNum = 0;
32 // if (badNum < 0) badNum = 0;
33 // ans = weekCount * (g + b);
34 // while (goodNum) {
35 // int delta = min(g, goodNum);
36 // ans += delta; goodNum -= delta;
37 // if (goodNum <= 0) break;
38 // badNum -= b;
39 // if (badNum < 0) badNum = 0;
40 // ans += b;
41 // }
42 // ans += badNum;
43 // printf("%lld\n", ans);
44 // }
45 // return 0;
46 // }
47
48 /* basic header */
49 #include <bits/stdc++.h>
50 /* define */
51 #define ll long long
52 #define dou double
53 #define pb emplace_back
54 #define mp make_pair
55 #define sot(a,b) sort(a+1,a+1+b)
56 #define rep1(i,a,b) for(int i=a;i<=b;++i)
57 #define rep0(i,a,b) for(int i=a;i<b;++i)
58 #define eps 1e-8
59 #define int_inf 0x3f3f3f3f
60 #define ll_inf 0x7f7f7f7f7f7f7f7f
61 #define lson (curpos<<1)
62 #define rson (curpos<<1|1)
63 /* namespace */
64 using namespace std;
65 /* header end */
66
67 int t;
68
69 int main() {
70 cin >> t;
71 while (t--) {
72 ll N, n, g, b; cin >> n >> g >> b;
73 N = n, n = n + 1 >> 1;
74 ll ans = (n / g) * (g + b) + n % g;
75 if (n % g == 0 && n / g) ans -= b;
76 cout << max(ans, N) << endl;
77 }
78 return 0;
79 }
C：
建无向图dfs即可
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 t;
21 vector<int>edge[26];
22 string s, ans;
23 bool used[26];
24
25 void dfs(int v) {
26 if (used[v]) return;
27 ans += char('a' + v);
28 used[v] = 1;
29 for (auto to : edge[v]) {
30 if (!used[to]) dfs(to);
31 }
32 }
33
34 int main() {
35 cin >> t;
36 while (t--) {
37 ans = "";
38 for (int i = 0; i < 26; i++) edge[i].clear();
39 memset(used, 0, sizeof(used));
40 cin >> s;
41 int n = s.size();
42 for (int i = 0; i < n - 1; i++) {
43 int a = s[i] - 'a', b = s[i + 1] - 'a';
44 edge[a].pb(b), edge[b].pb(a);
45 }
46 for (int i = 0; i < 26; i++) {
47 sort(edge[i].begin(), edge[i].end());
48 edge[i].erase(unique(edge[i].begin(), edge[i].end()), edge[i].end());
49 }
50 for (int i = 0; i < 26; i++)
51 if (!used[i] && edge[i].size() <= 1) dfs(i);
52 if (ans.size() < 26) {
53 puts("NO");
54 continue;
55 }
56 int flag = 1;
57 for (int i = 0; i < n - 1; i++) {
58 int pos1, pos2;
59 for (int j = 0; j < ans.size(); j++) {
60 if (ans[j] == s[i]) pos1 = j;
61 if (ans[j] == s[i + 1]) pos2 = j;
62 }
63 if (abs(pos1 - pos2) != 1) flag = 0;
64 }
65 if (!flag) puts("NO");
66 else printf("YES\n%s\n", ans.c_str());
67 }
68 }
D：
枚举2的幂，判断能否从低到高凑出n
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 ll n, sum;
21 int t, m, ans;
22 map<ll, int>cnt;
23
24 int main() {
25 scanf("%d", &t);
26 while (t--) {
27 cnt.clear();
28 sum = 0, ans = 0;
29 scanf("%lld%d", &n, &m);
30 for (int i = 0; i < m; i++) {
31 ll x; scanf("%lld", &x);
32 sum += x; cnt[x]++;
33 }
34 if (sum < n) {
35 puts("-1");
36 continue;
37 }
38 for (int i = 0; i < 63; i++) {
39 ll j = 1ll << i;
40 if (cnt[j] < ((n >> i) & 1)) {
41 ans++;
42 cnt[j] += 2;
43 cnt[j << 1] -= 1;
44 }
45 cnt[j << 1] += (cnt[j] - ((n >> i) & 1)) / 2;
46 }
47 printf("%d\n", ans);
48 }
49 return 0;
50 }
来源：https://www.cnblogs.com/JHSeng/p/12302944.html