比赛-Round (10 Jul)

1. 无线通讯网

#include <stdio.h>
#include <algorithm>
#include <math.h>

using namespace std;

typedef long long LL;

const int _N = 600;

LL P, S;
LL Dad[_N], dis[_N][_N], A[_N*_N], X[_N], Y[_N];
bool mk[_N];

LL _fun(LL val) { return val * val; }

LL GetDad(LL v) { return Dad[v] == v ? v : Dad[v] = GetDad(Dad[v]); }

bool Check(LL lim)
{
    LL i, j;
    for (i = 1; i <= P; ++i) Dad[i] = i, mk[i] = false;
    for (i = 1; i <= P; ++i)
        for (j = 1; j <= P; ++j)
            if (i != j && dis[i][j] <= A[lim]) {
                LL t1 = GetDad(i), t2 = GetDad(j);
                if (t1 != t2) Dad[t1] = t2;
            }
    LL cnt = 0;
    for (i = 1; i <= P; ++i) {
        LL tmp = GetDad(i);
        if (!mk[tmp]) mk[tmp] = true, ++cnt;
    }
    return cnt <= S;
}

int main()
{
    freopen("wireless.in", "r", stdin);
    freopen("wireless.out", "w", stdout);
    LL i, j, Acnt = 0;
    scanf("%lld%lld", &S, &P);
    for (i = 1; i <= P; ++i) scanf("%lld%lld", &X[i], &Y[i]);
    for (i = 1; i <= P; ++i)
        for (j = 1; j <= P; ++j)
            if (i != j) A[++Acnt] = dis[i][j] = _fun(X[i]-X[j]) + _fun(Y[i]-Y[j]);
    A[++Acnt] = 0;
    sort(A+1, A+1+Acnt);
    LL l = 1, r = Acnt;
    while (l <= r) {
        LL mid = l+r >> 1;
        if (Check(mid)) r = mid - 1;
        else l = mid + 1;
    }
    printf("%.2lf
", sqrt(A[l]));
    
    return 0;
}

2. 混合图

#include <stdio.h>
#include <vector>
#include <queue>

using namespace std;

const int _N = 120000;

queue<int> Q;
vector<int> G[_N];

int ind[_N], pos[_N];

inline void Ins(int a, int b) { G[a].push_back(b); ++ind[b]; return; }

int main()
{
    int N, i, M1, M2, a, b;
    scanf("%d%d%d", &N, &M1, &M2);
    for (i = 1; i <= M1; ++i)
        scanf("%d%d", &a, &b), Ins(a, b);
    for (i = 1; i <= N; ++i) {
        if (!ind[i]) Q.push(i);
        pos[i] = N+1;
    }
    int cnt = 0;
    while (!Q.empty()) {
        int t = Q.front();
        pos[t] = ++cnt;
        Q.pop();
        for (i = G[t].size()-1; i >= 0; --i)
            if(!--ind[G[t][i]]) Q.push(G[t][i]);
    }
    for (i = 1; i <= M2; ++i) {
        scanf("%d%d", &a, &b);
        if (pos[a] > pos[b]) swap(a, b);
        printf("%d %d
", a, b);
    }
    return 0;
}

3. 小K的农场

非常重要。学到了新操作：SPFA 的 SLF, LLL 优化，以及在判负环时的 DFS 优化，还有权值无意义时（只判负环时）的 DFS, dis[i] = 0 优化。

详细见 SPFA 模板那篇随笔（http://www.cnblogs.com/ghcred/p/8051261.html）

#include <stdio.h>
#include <queue>

using namespace std;

const int _N = 12000;
const int INF = 1e9;

struct edge {
    int v, w;
    edge(int v, int w):
        v(v), w(w) { }
};

vector<edge> G[_N];
int N, M;
int dis[_N], cnt[_N];
bool mk[_N];
deque<int> Q;

bool SPFA(int p)
{
    bool flag = false;
    mk[p] = true;
    for (int i = G[p].size()-1; i >= 0; --i) {
        edge v = G[p][i];
        if (dis[v.v] > dis[p]+v.w) {
            dis[v.v] = dis[p]+v.w;
            if (!mk[v.v]) {
                if (SPFA(v.v)) { flag = true; break; }
            } else {
                flag = true;
                break;
            }
        }
    }
    mk[p] = false;
    return flag;
}

void Ins(int t0, int t1, int t2) { G[t0].push_back(edge(t1, t2)); return; }

int main()
{
    int i;
    scanf("%d%d", &N, &M);
    for (i = 1; i <= M; ++i) {
        int a, b, c, ins;
        scanf("%d%d%d", &ins, &a, &b);
        if (ins == 1)
            scanf("%d", &c), Ins(b, a, c);
        else if (ins == 2)
            scanf("%d", &c), Ins(a, b, -c);
        else
            Ins(a, b, 0), Ins(b, a, 0);
    }
    for (i = 1; i <= N; ++i)
        if (SPFA(i)) break;
    if (i != N+1) printf("No
");
    else printf("Yes
");
    return 0;
}