Submission #1112298

#	Time	Username	Problem	Language	Result	Execution time	Memory
1112298		Mike_Vu	Construction Project 2 (JOI24_ho_t2)	C++14	100 / 100	199 ms	24584 KiB

Main

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double dou;
#define pii pair<int, int>
#define fi first
#define se second
#define pb push_back
#define MASK(x) (1LL<<(x))
#define BITj(x, j) (((x)>>(j))&1)

template<typename T> bool maximize(T &x, const T &y) {
    if (x < y) {x = y; return 1;}
    return 0;
}
template<typename T> bool minimize(T &x, const T &y) {
    if (x > y) {x = y; return 1;}
    return 0;
}

const int maxn = 2e5+5;
int n, m, s, t;
ll len, bound, ans = 0;
vector<pii> a[maxn];
ll dis1[maxn], dis2[maxn];

void dijkstra(int s, ll dis[]) {
    priority_queue<pair<ll, int>> q;
    q.push({0, s});
    dis[s] = 0;
    while (!q.empty()) {
        int u = q.top().se;
        ll w = -q.top().fi;
        q.pop();
        if (w != dis[u]) continue;
        for (int i = 0; i < (int)a[u].size(); i++) {
            int v = a[u][i].fi, w = a[u][i].se;
            if (minimize(dis[v], dis[u]+w)) {
                q.push({-dis[v], v});
            }
        }
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
//    #define name "task"
//    if (fopen(name".inp", "r")) {
//        freopen(name".inp", "r", stdin);
//        freopen(name".out", "w", stdout);
//    }
    cin >> n >> m >> s >> t >> len >> bound;
    for (int i = 1; i <= m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        a[u].pb({v, w});
        a[v].pb({u, w});
    }
    //dijkstra
    memset(dis1, 0x3f, sizeof(dis1));
    dijkstra(s, dis1);
    memset(dis2, 0x3f, sizeof(dis2));
    dijkstra(t, dis2);
    //check case 1
    if (dis1[t] <= bound) {
        cout << ((ll)n*(n-1)/2);
        return 0;
    }
    //cal + bs
    vector<pair<ll, int>> val;
    for (int i = 1; i <= n; i++) {
        val.pb({dis1[i], i});
    }
    sort(val.begin(), val.end());
    for (int i = 1; i < n; i++) {
        int u = val[i].se;
        //binsearch with bound
        ll curbound = bound-len-dis2[u];
        if (curbound < 0) continue;
        int k = -1;
        for (int j = n>>1; j; j >>= 1) {
            while (k+j < n && val[k+j].fi <= curbound) k += j;
        }
        ans += k+1;
    }
    //output
    cout << ans;
}
/*
7 8
6 7 1 2
1 2 1
1 6 1
2 3 1
2 4 1
3 5 1
3 7 1
4 5 1
5 6 1

3 2
1 3 1 2
1 2 1
2 3 1

6 4
2 5 1000000000 1
1 2 1000000000
2 3 1000000000
2 4 1000000000
5 6 1000000000

18 21
4 8 678730772 3000000062
5 13 805281073
8 17 80983648
3 8 996533440
10 16 514277428
2 5 57914340
6 11 966149890
8 12 532734310
2 9 188599710
2 3 966306014
12 16 656457780
16 18 662633078
1 15 698078877
2 8 665665772
2 6 652261981
14 15 712798281
7 13 571169114
13 14 860543313
6 7 454251187
9 14 293590683
6 14 959532841
3 11 591245645
*/

• Subtask 1: 8 / 8
• Subtask 2: 16 / 16
• Subtask 3: 29 / 29
• Subtask 4: 47 / 47