Codeforces 545E【最小树形图】

/* I will wait for you */

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <string>
#define make make_pair
#define fi first
#define se second

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef map<int, int> mii;

const int maxn = 300010;
const int maxm = 1010;
const int maxs = 26;
const int inf = 0x3f3f3f3f;
const int P = 1000000007;
const double error = 1e-9;

inline ll read()
{
ll x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9')
f = (ch == '-' ? -1 : 1), ch = getchar();
while (ch >= '0' && ch <= '9')
x = x * 10 + ch - '0', ch = getchar();
return x * f;
}

struct edge
{
int u, v; ll w; int next, pos;
} e[2 * maxn];

int n, m, s, cnt, head[maxn], vis[maxn], fa[maxn];
ll ans, dis[maxn];

void insert(int u, int v, ll w, int pos)
{
e[cnt] = (edge) {u, v, w, head[u], pos}, head[u] = cnt++;
e[cnt] = (edge) {v, u, w, head[v], pos}, head[v] = cnt++;
}

void spfa()
{
for (int i = 1; i <= n; i++)
dis[i] = (ll) inf * inf;

queue<int> q; q.push(s), dis[s] = 0;

while (!q.empty()) {
int u = q.front();
q.pop(), vis[u] = 0;

for (int i = head[u]; i != -1; i = e[i].next) {
int v = e[i].v;
if (dis[v] > dis[u] + e[i].w) {
dis[v] = dis[u] + e[i].w;
if (!vis[v])
vis[v] = 1, q.push(v);
}
}
}
}

bool cmp(edge a, edge b)
{
ll disa = max(dis[a.u], dis[a.v]);
ll disb = max(dis[b.u], dis[b.v]);
return disa < disb || disa == disb && a.w < b.w;
}

int find(int u)
{
return u == fa[u] ? u : fa[u] = find(fa[u]);
}

vector<int> num;

int main()
{
n = read(), m = read();

memset(head, -1, sizeof head);
for (int i = 1; i <= m; i++) {
int u = read(), v = read(); ll w = read();
insert(u, v, w, i);
}

s = read(), spfa();

sort(e, e + cnt, cmp);

for (int i = 1; i <= n; i++)
fa[i] = i;

for (int i = 0; i < cnt; i++) {
int u = e[i].u, v = e[i].v;
if (abs(dis[u] - dis[v]) == e[i].w) {
int fu = find(u), fv = find(v);
if (fu != fv) {
ans += e[i].w, fa[fu] = fv;
num.push_back(e[i].pos);
}
}
}

printf("%I64d\n", ans);

for (int i = 0; i < num.size(); i++)
printf("%d ", num[i]);

return 0;
}