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。

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

const int maxn=1e5+10;
char s[maxn],t[maxn];

int main() {
    scanf("%s",s+1);
    scanf("%s",t+1);
    int ans=0;
    for (int i=1;i<=3;i++)
        ans+=s[i]==t[i];
    printf("%d
",ans);
    return 0;
}

B：

枚举就好了。

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

int a, b;

int main() {
    while (scanf("%d%d", &a, &b) != EOF) {
        int curr=1,ans=0;
        while (curr<b){
            curr+=a-1;
            ans++;
        }
        printf("%d
",ans);
    }
    return 0;
}

C：

倒着扫一次就好了。

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

const int maxn = 1e5 + 10;
int n, a[maxn];

int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
    int ans = 0, cnt = 0;
    for (int i = n; i > 1; i--) {
        if (a[i] <= a[i - 1]) cnt++;
        else {
            ans = max(ans, cnt);
            cnt = 0;
        }
    }
    ans = max(ans, cnt);
    printf("%d
", ans);
    return 0;
}

D：

打个表就知道答案。

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

ll n;

int main() {
    scanf("%lld", &n);
    printf("%lld
", (1ll + (n - 1)) * (n - 1) / 2);
    return 0;
}

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。

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

int n;
vector<pair<ll, ll>> v;

int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        pair<ll, ll> p; scanf("%lld%lld", &p.first, &p.second);
        if (p.first || p.second) v.pb(p);
    }
    n = (int)v.size();
    sort(v.begin(), v.end(), [&](pair<ll, ll> a, pair<ll, ll> b) {
        return atan2(a.second, a.first) < atan2(b.second, b.first);
    });
    ll ans = 0;
    for (int i = 0; i < n; i++) {
        int j = i; ll x = 0, y = 0;
        for (int k = 0; k < n; k++) {
            x += v[j].first; y += v[j].second;
            ans = max(ans, x * x + y * y);
            if (++j == n) j = 0;
        }
    }
    printf("%.15f
", sqrt(ans));
    return 0;
}