AtCoder Beginning Contest 139

很傻的一场。

题目链接：https://atcoder.jp/contests/abc139/

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A：

傻题。

 1 /* basic header */
 2 #include 
 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;i11 #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=1e5+10;
21 char s[maxn],t[maxn];
22 
23 int main() {
24     scanf("%s",s+1);
25     scanf("%s",t+1);
26     int ans=0;
27     for (int i=1;i<=3;i++)
28         ans+=s[i]==t[i];
29     printf("%d\n",ans);
30     return 0;
31 }

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B：

枚举就好了。

 1 /* basic header */
 2 #include 
 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;i11 #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, b;
21 
22 int main() {
23     while (scanf("%d%d", &a, &b) != EOF) {
24         int curr=1,ans=0;
25         while (curr<b){
26             curr+=a-1;
27             ans++;
28         }
29         printf("%d\n",ans);
30     }
31     return 0;
32 }

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C：

倒着扫一次就好了。

 1 /* basic header */
 2 #include 
 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;i11 #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 = 1e5 + 10;
21 int n, a[maxn];
22 
23 int main() {
24     scanf("%d", &n);
25     for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
26     int ans = 0, cnt = 0;
27     for (int i = n; i > 1; i--) {
28         if (a[i] <= a[i - 1]) cnt++;
29         else {
30             ans = max(ans, cnt);
31             cnt = 0;
32         }
33     }
34     ans = max(ans, cnt);
35     printf("%d\n", ans);
36     return 0;
37 }

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D：

打个表就知道答案。

 1 /* basic header */
 2 #include 
 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;i11 #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;
21 
22 int main() {
23     scanf("%lld", &n);
24     printf("%lld\n", (1ll + (n - 1)) * (n - 1) / 2);
25     return 0;
26 }

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E：

队友说是模拟。(完全不想写

F：

sort一遍所有向量之后以每个向量为起点，n方暴力验证。

 1 /* basic header */
 2 #include 
 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;i11 #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 n;
21 vector> v;
22 
23 int main() {
24     scanf("%d", &n);
25     for (int i = 1; i <= n; i++) {
26         pair p; scanf("%lld%lld", &p.first, &p.second);
27         if (p.first || p.second) v.pb(p);
28     }
29     n = (int)v.size();
30     sort(v.begin(), v.end(), [&](pair a, pair b) {
31         return atan2(a.second, a.first) < atan2(b.second, b.first);
32     });
33     ll ans = 0;
34     for (int i = 0; i < n; i++) {
35         int j = i; ll x = 0, y = 0;
36         for (int k = 0; k < n; k++) {
37             x += v[j].first; y += v[j].second;
38             ans = max(ans, x * x + y * y);
39             if (++j == n) j = 0;
40         }
41     }
42     printf("%.15f\n", sqrt(ans));
43     return 0;
44 }

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