Submission #683465

#	Time	Username	Problem	Language	Result	Execution time	Memory
683465		nguyentunglam	Swapping Cities (APIO20_swap)	C++14	53 / 100	420 ms	40932 KiB

swap

#include<bits/stdc++.h>
#define fi first
#define se second
#define endl "\n"
#define ii pair<int, int>
using namespace std;
const int N = 1e5 + 10;
int lab[N], order[N], deg[N], noline[N], mx[N], h[N];
int par[18][N], f[18][N];
int cur;
vector<int> lst[N];
vector<pair<int, int> > adj[N];
int root(int v) {
    return lab[v] < 0 ? v : lab[v] = root(lab[v]);
}
void update(int u) {
    if (mx[u] <= 2) return;
    for(int j : lst[u]) noline[j] = cur;
    lst[u].clear();
}
bool join(int u, int v) {
    u = root(u); v = root(v);
    if (u == v) return 0;
    if (lab[u] > lab[v]) swap(u, v);
    mx[u] = max(mx[u], mx[v]);
    lab[u] += lab[v];
    for(int j : lst[v]) lst[u].push_back(j);
    lab[v] = u;
    return 1;
}
void dfs(int u) {
    for(auto [v, w] : adj[u]) if (v != par[0][u]) {
        par[0][v] = u;
        f[0][v] = w;
        for(int j = 1; j <= 17; j++) {
            int p = par[j - 1][v];
            par[j][v] = par[j - 1][p];
            f[j][v] = max(f[j - 1][v], f[j - 1][p]);
        }
        h[v] = h[u] + 1;
        dfs(v);
    }
}
int lca(int u, int v) {
    int ret = 0;
    if (h[u] < h[v]) swap(u, v);
    int delta = h[u] - h[v];
    for(int j = 0; j <= 17; j++) if ((delta >> j) & 1) {
        ret = max(ret, f[j][u]);
        u = par[j][u];
    }
    if (u == v) return ret;
    for(int j = 17; j >= 0; j--) if (par[j][u] != par[j][v]) {
        ret = max(ret, f[j][u]);
        ret = max(ret, f[j][v]);
        u = par[j][u];
        v = par[j][v];
    }
    return max({ret, f[0][u], f[0][v]});
}
void init(int n, int m, vector<int> u, vector<int> v, vector<int> w) {
    for(int i = 0; i < n; i++) {
        lab[i] = -1;
        lst[i].push_back(i);
    }
    for(int i = 0; i < m; i++) order[i] = i;
    sort(order, order + m, [&] (int &x, int &y) {
         return w[x] < w[y];
         });
    for(int j = 0; j < m; j++) {
        int i = order[j];
        cur = w[i];
        if (join(u[i], v[i])) {
            adj[u[i]].push_back({v[i], w[i]});
            adj[v[i]].push_back({u[i], w[i]});
        }
        else mx[root(u[i])] = 3;
        int r = root(u[i]);
        mx[r] = max(mx[r], max(++deg[u[i]], ++deg[v[i]]));
        update(r);
    }
    dfs(0);
}
int getMinimumFuelCapacity(int x, int y) {
    if (!noline[x]) return -1;
    return max(noline[x], lca(x, y));
}
//int main() {
//    #define task ""
//    cin.tie(0) -> sync_with_stdio(0);
//    if (fopen ("task.inp", "r")) {
//        freopen ("task.inp", "r", stdin);
//        freopen ("task.out", "w", stdout);
//    }
//    if (fopen (task".inp", "r")) {
//        freopen (task".inp", "r", stdin);
//        freopen (task".out", "w", stdout);
//    }
////    int u[1000] = {0, 0, 1, 1, 1, 2};
////    int v[1000] = {1, 2, 2, 3, 4, 3};
////    int w[1000] = {4, 4, 1, 2, 10, 3};
//    vector<int> u = {0, 0};
//    vector<int> v = {1, 2};
//    vector<int> w = {5, 5};
//    init(3, 2, u, v, w);
//    cout << getMinimumFuelCapacity(1, 2);
//}

Compilation message (stderr)

swap.cpp: In function 'void dfs(int)':
swap.cpp:32:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   32 |     for(auto [v, w] : adj[u]) if (v != par[0][u]) {
      |              ^

• Subtask 1: 6 / 6
• Subtask 2: 7 / 7
• Subtask 3: 17 / 17
• Subtask 4: 0 / 20
• Subtask 5: 23 / 23
• Subtask 6: 0 / 27