2017 CCPC 哈尔滨

D

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
const int maxn = 1e3+5;
bool vis[maxn];
vector<int> e[maxn];
int dist[maxn];

void dfs(int id,int fa){
	for(auto ep:e[id]){
		if(ep==fa) continue;
		dist[ep]=dist[id]+1;
		dfs(ep,id);
	}
}

int main(){
	//freopen("in.txt","r",stdin);
	int T,n,m,x,y;
	cin>>T;
	while(T--){
		scanf("%d%d",&n,&m);
		memset(vis,0,sizeof vis);
		for(int i=1;i<=n;i++) e[i].clear();
		for(int i=1;i<=m;i++){
			scanf("%d",&x);
			vis[x]=1;
		}
		for(int i=1;i<n;i++){
			scanf("%d%d",&x,&y);
			e[x].push_back(y);
			e[y].push_back(x);
		}
		int rt=1;
		for(;rt<=n;rt++)
			if(vis[rt]) break;
		dist[rt]=0;
		dfs(rt,-1);
		int D=0,id=0;
		for(int i=1;i<=n;i++)
			if(vis[i]&&dist[i]>D){
				D=dist[i];
				id=i;
			}
		dist[id]=0;
		dfs(id,-1);
		D=0;
		for(int i=1;i<=n;i++)
			if(vis[i]&&dist[i]>D)
				D=dist[i];
		printf("%d.00
",D/2);
	}
	return 0;
}

F

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main(){
	//freopen("in.txt","r",stdin);
	int T,n;
	cin>>T;
	while(T--){
		scanf("%d",&n);
		int t=n/2;
		if(n%2==0){
			for(int i=1;i<=n/2;i++){
				if(i!=1) printf(" ");
				printf("%d %d",i,t+i);
			}
			puts("");
		} else {
			t++;
			for(int i=1;i<=n/2;i++){
				if(i!=1) printf(" ");
				printf("%d %d",i,t+i);
			}
			printf(" %d
",t);
		}
	}
	return 0;
}

H

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

vector<ll> v;
const int maxn = 1e5+5;
int a[maxn],n;
int MOD[maxn];

int main(){
	//freopen("in.txt","r",stdin);
	int T;
	cin>>T;
	while(T--){
		ll s=0;
		scanf("%d",&n);
		for(int i=1;i<=n;i++){
			scanf("%d",a+i);
			s+=a[i];
		}
		v.clear();
		for(ll i=2;i*i<=s;i++){
			if(s%i==0){
				v.push_back(i);
				while(s%i==0)
					s/=i;
			}
		}
		if(s!=1) v.push_back(s);
		ll ans=100000000000000ll;
		for(auto x:v){
			ll res=0;
			ll tot=0;
			for(int i=1;i<=n;i++)
				MOD[i]=a[i]%x,tot+=MOD[i];
			sort(MOD+1,MOD+1+n);
			int id=n;
			while(tot!=0&&id>=1){
				res+=x-MOD[id--];
				tot-=x;
			}
			if(tot==0&&res<ans)
				ans=res;
		}
		printf("%lld
",ans);
	}
	return 0;
}

J

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
const int mod = 1e9 + 7;

inline ll power(ll a, ll n, ll p) {
	ll ret = 1; ll now = a;
	while (n != 0) {
		if (n & 1)
			ret = ret * now % p;
		now = now * now % p;
		n >>= 1;
	}
	return ret;
}

inline ll gcd(ll a, ll b) {
	return b == 0 ? a : gcd(b, a % b);
}

int main() {
	//freopen("in.txt","r",stdin);
	int T, n, d;
	cin >> T;
	while (T--) {
		scanf("%d%d", &n, &d);
		ll a, b;
		if (d == 1) {
			a = (n + 2);
			b = 4ll;
		} else {
			a = 3ll * (n + 2);
			b = 8ll;
		}
		ll g = gcd(a, b);
		a /= g; b /= g;
		//cout << a << " " << b << endl;
		cout << (ll)a*power(b, mod - 2, mod) % mod << endl;
	}
	return 0;
}

L

hdu 6241

M

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const double eps = 1e-3;
const int maxn = 1e5 + 5;
int T, n;
struct vec {
    double x, y;
    vec() {}
    vec(double _x, double _y) {x = _x; y = _y;}
};
struct circle {
    double x, y;
    double r;
};
vec p[maxn];
int a, b, c, cnt;
double d;
double mx = 1e9;

int sgn(double x) {
    if (x > eps) return 1;
    if (x < -eps) return -1;
    return 0;
}

double dist(vec a, vec b) {
    double tx = a.x - b.x;
    double ty = a.y - b.y;
    return sqrt(tx * tx + ty * ty);
}

int rando() {
    return (rand() << 15 ) | rand();
}

circle get(vec a, vec b, vec c) {
    circle ret;
    double A1, A2, B1, B2, C1, C2, tmp;
    A1 = a.x - b.x;
    B1 = a.y - b.y;
    C1 = (a.x * a.x - b.x * b.x + a.y * a.y - b.y * b.y) / 2;
    A2 = c.x - b.x;
    B2 = c.y - b.y;
    C2 = (c.x * c.x - b.x * b.x + c.y * c.y - b.y * b.y) / 2;
    tmp = A1 * B2 - A2 * B1;
    ret.x = (C1 * B2 - C2 * B1) / tmp;
    ret.y = (A1 * C2 - A2 * C1) / tmp;
    ret.r = dist(vec(ret.x, ret.y), a);
    return ret;
}

bool sameline(vec a, vec b, vec c) {
    double x1, y1, x2, y2;
    x1 = a.x - b.x;
    y1 = a.y - b.y;
    x2 = a.x - c.x;
    y2 = a.y - c.y;
    double Cx = x1 * y2 - x2 * y1;
    if (sgn(Cx) == 0) return 1;
    return 0;
}

int main() {
    freopen("in.txt", "r", stdin);
    srand(time(0));
    cin >> T;
    while (T--) {
        scanf("%d", &n);
        for (int i = 1; i <= n; i++)
            scanf("%lf%lf", &p[i].x, &p[i].y);
        if (n == 1) {
            printf("%lf %lf %lf
", p[1].x, p[1].y, 0.0);
        } else if (n <= 4) {
            printf("%lf %lf %lf
", (p[1].x + p[2].x) / 2.0, (p[1].y + p[2].y) / 2.0, dist(vec((p[1].x + p[2].x) / 2.0, (p[1].y + p[2].y) / 2.0), p[2]));
        } else {
            circle ans;
            for (;;) {
                int a = (rando() % n + n) % n + 1;
                while ((b = (rando() % n + n) % n + 1) == a);
                while ((c = (rando() % n + n) % n + 1) == b || c == a);
                if (sameline(p[a], p[b], p[c])) continue;
                //cout << a << " " << b << " " << c << endl;
                ans = get(p[a], p[b], p[c]);
                if (fabs(ans.x) > mx || fabs(ans.y) > mx || ans.r > mx)continue;
                cnt = 0;
                for (int j = 1; j <= n; j++) {
                    d = dist(vec(ans.x, ans.y), p[j]);
                    if (sgn(d - ans.r) == 0)
                        cnt++;
                }
                if (cnt >= (n / 2 + (n % 2 == 1))) {
                    // if (sgn(ans.x) == 0) ans.x = 0.0;
                    // if (sgn(ans.y) == 0) ans.y = 0.0;
                    printf("%.6f %.6f %.6f
", ans.x, ans.y, ans.r);
                    break;
                }
            }
        }
    }
    return 0;
}