Submission #1279694

#	Time	Username	Problem	Language	Result	Execution time	Memory
1279694		nmhung	LOSTIKS (INOI20_lostiks)	C++20	100 / 100	1230 ms	202028 KiB

Main

#include <bits/stdc++.h>

using namespace std;

mt19937_64 rd(chrono::steady_clock::now().time_since_epoch().count());

#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define rf if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout);}
//#define in ({int x = 0; int c = getchar(), n = 0; for(; !isdigit(c); c = getchar()) n = (c == '-'); for(; isdigit(c); c = getchar()) x = x * 10 + c - '0'; n ? -x : x;})

#define bit(i, mask) (((mask) >> (i)) & 1)
#define on(i, mask) ((mask) | (1LL << (i)))
#define off(i, mask) ((mask) & (~(1LL << (i))))

#define ll long long
#define fi first
#define se second
#define pii pair<int, int>
#define vi vector<int>
#define all(a) (a).begin(), (a).end()
#define len(x) ((int)(x).size())
#define pb push_back
#define endl '\n'

#define name "treemaze"

template<typename T1, typename T2> bool mini(T1 &a, T2 b)
    {if(a > b) a = b; else return 0; return 1;}
template<typename T1, typename T2> bool maxi(T1 &a, T2 b)
    {if(a < b) a = b; else return 0; return 1;}

const int mod = 1e9 + 7;
const int inf = 1e9 + 9;
const ll  oo  = 1e18l + 7;
const int M   = 5e5 + 6;
const int N   = 1e6 + 6;
const int LOG = 31 - __builtin_clz(N);

int n, m, S, T;
vector<pii> adj[N];
int key[50], node[50], h[N], val[N], go[N];
int par[N], sz[N], id[N], head[N], cnt = 0;
int tin[N], tout[N], cntDfs = 0;
int dp[1 << 20][20];

void inp(){
    cin >> n >> S >> T;
    m = 0;
    for(int i = 1; i < n; i++){
        int u, v, h; cin >> u >> v >> h;
        int w = 0;
        if(h){
            w = (1 << m);
            key[m] = h;
            node[m << 1] = u; node[m << 1 | 1] = v;
            m++;
        }
        adj[u].pb({v, w});
        adj[v].pb({u, w});
    }
}

void dfs(int u, int pre){
    sz[u] = 1;
    tin[u] = ++cntDfs;
    for(auto it : adj[u]){
        int v = it.fi, w = it.se;
        if(v == pre) continue;
        par[v] = u;
        h[v] = h[u] + 1;
        val[v] = val[u] ^ w;
        dfs(v, u);
        sz[u] += sz[v];
    }
    tout[u] = cntDfs;
}

void Hld(int u, int pre, int top){
    id[u] = ++cnt;
    head[u] = top;

    int nxt = -1;
    for(auto it : adj[u]){
        int v = it.fi;
        if(v == pre) continue;
        if(nxt == -1 || sz[nxt] < sz[v]) nxt = v;
    }
    if(nxt == -1) return;
    Hld(nxt, u, top);
    for(auto it : adj[u]){
        int v = it.fi;
        if(v == pre || v == nxt) continue;
        Hld(v, u, v);
    }
}

int lca(int u, int v){
    while(head[u] != head[v]){
        if(id[head[u]] > id[head[v]]) swap(u, v);
        v = par[head[v]];
    }
    return (h[u] > h[v]) ? v : u;
}

int dist(int u, int v){
    return h[u] + h[v] - 2 * h[lca(u, v)];
}

bool insub(int u, int v){
    return tin[u] <= tin[v] && tout[v] <= tout[u];
}

bool canGo(int u, int v, int mask){
    int nmask = val[v] ^ val[u];
    return ((nmask & mask) == nmask);
}

void proc(){
    dfs(1, 1);
    Hld(1, 1, 1);

    if(canGo(S, T, 0)){
        cout << dist(S, T) << endl;
        return;
    }

    for(int i = 0; i < m; i++){
        int u = node[i << 1], v = node[i << 1 | 1];
        if(h[u] > h[v]) swap(u, v);
        go[i] = insub(v, S) ? v : u;
    }

    for(int mask = 0; mask < (1 << m); mask++) for(int i = 0; i < m; i++) dp[mask][i] = inf;
    for(int i = 0; i < m; i++){
        if(canGo(S, key[i], 0) && canGo(key[i], go[i], 0))
            dp[1 << i][i] = dist(S, key[i]) + dist(key[i], go[i]);
    }

    for(int mask = 0; mask < (1 << m); mask++){
        for(int i = 0; i < m; i++){
            if(dp[mask][i] == inf) continue;
            for(int j = 0; j < m; j++){
                if(bit(j, mask)) continue;
                if(canGo(go[i], key[j], mask) && canGo(key[j], go[j], mask))
                    mini(dp[mask | (1 << j)][j], dp[mask][i] + dist(go[i], key[j]) + dist(key[j], go[j]));
            }
            
        }
    }
    int ans = inf;
    for(int mask = 0; mask < (1 << m); mask++){
        for(int i = 0; i < m; i++){
            if(dp[mask][i] == inf) continue;
            if(canGo(go[i], T, mask)) mini(ans, dp[mask][i] + dist(go[i], T));
        }
    }
    cout << (ans == inf ? -1 : ans);
}

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    
    rf

    int test = 1;
    //cin >> test;

    while(test--){
        inp();
        proc();
    }
    
    cerr << "Time elapsed: " << TIME << "s" << endl;
    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:8:47: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 | #define rf if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout);}
      |                                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:163:5: note: in expansion of macro 'rf'
  163 |     rf
      |     ^~
Main.cpp:8:80: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 | #define rf if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout);}
      |                                                                         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:163:5: note: in expansion of macro 'rf'
  163 |     rf
      |     ^~

• Subtask 1: 23 / 23
• Subtask 2: 36 / 36
• Subtask 3: 41 / 41