Create L14-2.cpp

L14-2.cpp

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+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+typedef pair<ll, ll> pl;
+
+#define PUB push_back
+#define fi first
+#define se second
+
+const int LOG_TWO = log2(2e5+5);
+
+struct query{
+	int x, y, z;
+	query(): x(0), y(0), z(0) {}
+	query(int _x, int _y, int _z): x(_x), y(_y), z(_z) {}
+};
+
+int Q, N = 1;
+int depth[200005], sparse[LOG_TWO+1][200005];
+vector<int>adjL[200005];
+vector<query>data;
+
+void DFS(int prn, int pos, int d){
+	depth[pos] = d;
+	sparse[0][pos] = prn;
+
+	for(int nxt:adjL[pos])
+		DFS(pos, nxt, d+1);
+}
+
+int find_LCA(int u, int v){
+	if(depth[u] < depth[v]) swap(u, v);
+
+	for(int i=LOG_TWO;i>=0;i--){
+		if(depth[sparse[i][u]] >= depth[v])
+			u = sparse[i][u];
+	}
+
+	if(u == v) return u;
+
+	for(int i=LOG_TWO;i>=0;i--){
+		if(sparse[i][u] != sparse[i][v]){
+			u = sparse[i][u];
+			v = sparse[i][v];
+		}
+	}
+
+	return sparse[0][u];
+}
+
+int main(){
+	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
+	memset(depth, -1, sizeof depth);
+	memset(sparse, -1, sizeof sparse);
+
+	cin >> Q;
+	while(Q--){
+		int id, x, y, z;
+		cin >> id >> x;
+		if(id == 1) adjL[x].PUB(++N);
+		else{
+			cin >> y >> z;
+			data.PUB(query(x, y, z));
+		}
+	}
+
+	// Build sparse table for LCA
+	DFS(-1, 1, 0);
+	for(int i=1;i<=LOG_TWO;i++)
+		for(int j=1;j<=N;j++)
+			if(sparse[i-1][j] != -1)
+				sparse[i][j] = sparse[i-1][sparse[i-1][j]];
+
+	// Solve query 
+	for(query elm:data){
+		int xy = find_LCA(elm.x, elm.y),
+			xz = find_LCA(elm.x, elm.z),
+			yz = find_LCA(elm.y, elm.z);
+
+		if(xy == xz && xz == yz) cout << xy << endl;
+		else if(xz == xy) cout << yz << endl;
+		else if(yz == xy) cout << xz << endl;
+		else if(xz == yz) cout << xy << endl;
+	}
+}