SGU145 Strange People

SGU145 Strange People

题目大意

算法思路

时间复杂度: O(KN3)O(KN^3)

代码

/**
* Copyright © 2015 Authors. All rights reserved.
*
* FileName: 145.cpp
* Author: Beiyu Li <sysulby@gmail.com>
* Date: 2015-06-18
*/
#include <bits/stdc++.h>

using namespace std;

#define rep(i,n) for (int i = 0; i < (n); ++i)
#define For(i,s,t) for (int i = (s); i <= (t); ++i)
#define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)

typedef long long LL;
typedef pair<int, int> Pii;

const int inf = 0x3f3f3f3f;
const LL infLL = 0x3f3f3f3f3f3f3f3fLL;

const int maxn = 100 + 5;

class Yen {
struct Path {
int w, dev;
vector<int> v;
bitset<maxn> blc;
bool operator<(const Path &p) const { return w > p.w; }
} p, q;
int n, s, t, w[maxn][maxn];
bitset<maxn> blc[maxn];
int dis[maxn], pre[maxn];
bool vis[maxn];

bool dijkstra(Path &ret, int d)
{
memset(pre, -1, sizeof(pre));
memset(vis, false, sizeof(vis));
memset(dis, 0x3f, sizeof(dis)); dis[s] = 0;
for (int i = 0; i < d - 1; ++i) {
int u = p.v[i], v = p.v[i+1];
vis[u] = true; dis[v] = dis[u] + w[u][v], pre[v] = u;
}
for (int i = 0; i < n; ++i) {
int u = -1;
for (int v = 0; v < n; ++v) if (!vis[v])
if (u == -1 || dis[v] < dis[u]) u = v;
if (u == -1 || dis[u] == inf) break; vis[u] = true;
for (int v = 0; v < n; ++v) if (!vis[v]) {
if (blc[u][v] || blc[v][u]) continue;
if (dis[u] + w[u][v] < dis[v])
dis[v] = dis[u] + w[u][v], pre[v] = u;
}
}
ret.w = dis[t]; ret.v.clear(); ret.blc.reset();
for (int u = t; ~u; u = pre[u]) ret.v.push_back(u);
reverse(ret.v.begin(), ret.v.end());
return dis[t] != inf;
}

public:
void init(int n)
{
this->n = n;
memset(w, 0x3f, sizeof(w));
}

void add_edge(int u, int v, int w)
{
this->w[u][v] = w;
}

bool find_kth(int src, int trg, int k)
{
s = src, t = trg;
priority_queue<Path> que;
for (int u = 0; u < n; ++u) blc[u].reset();
if (!dijkstra(p, 0)) return false;
p.dev = 1; p.blc.set(p.v[1]); que.push(p);
for (int i = 0; i < k; ++i) {
if (que.empty()) return false;
p = que.top(); que.pop();
for (int u = 0; u < n; ++u) blc[u].reset();
for (int d = p.dev; d < p.v.size(); ++d) {
int u = p.v[d-1];
d ^ p.dev? blc[u].set(p.v[d]): blc[u] = p.blc;
if (!dijkstra(q, d)) continue;
d ^ p.dev? q.blc.set(p.v[d]): q.blc = p.blc;
q.dev = d; q.blc.set(q.v[d]); que.push(q);
}
}
printf("%d %d\n", p.w, (int)p.v.size());
for (int i = 0; i < p.v.size(); ++i)
printf("%d%c", p.v[i] + 1, " \n"[i==p.v.size()-1]);
return true;
}
} grp;

int main()
{
int n, m, k, s, t;
scanf("%d%d%d", &n, &m, &k);
grp.init(n);
while (m--) {
int u, v, w;
scanf("%d%d%d", &u, &v, &w);
--u, --v;
grp.add_edge(u, v, w);
grp.add_edge(v, u, w);
}
scanf("%d%d", &s, &t);
--s, --t;
grp.find_kth(s, t, k);

return 0;
}