CF797D AC

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#define dbg(...) logger(#__VA_ARGS__, __VA_ARGS__)
template <typename... Args> void logger(string vars, Args &&... values)
{
    cerr << vars << " = ";
    string delim = "";
    (..., (cerr << delim << values, delim = ", "));
    cerr << endl;
}

template <class T> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m)); }
template <class T> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n)); }
template <class T, T init> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m, init)); }
template <class T, T init> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n, init)); }

template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;
using pii = pair<int, int>;
using vl = vector<ll>;
using vi = vector<int>;
using a2i = array<int, 2>;

int ans = 0;
int n;
a2i pts[100003];
ll val[100003];
map<int, int> vcnt;

void dfs(int u, ll lb, ll ub)
{
    if (lb > ub)
        return;
    if (u < 0)
        return;
    if (lb <= val[u] && val[u] <= ub)
        ans += vcnt[val[u]];
    dfs(pts[u][0], lb, min(ub, val[u] - 1));
    dfs(pts[u][1], max(lb, val[u] + 1), ub);
}

int main(int argc, char **argv)
{
    cin >> n;
    int x, l, r;
    vi noroot(n + 1);
    for (int i = 1; i <= n; ++i) {
        cin >> x >> l >> r, pts[i][0] = l, pts[i][1] = r, val[i] = x, vcnt[x]++;
        if (l != -1)
            noroot[l] = 1;
        if (r != -1)
            noroot[r] = 1;
    }
    int root = 0;
    for (int i = 1; i <= n; ++i)
        if (noroot[i] == 0) {
            root = i;
            break;
        }
    dfs(root, LLONG_MIN / 2, LLONG_MAX / 2);
    cout << n - ans << endl;
    return 0;
};