Merge pull request #137 from Aakanksha2518/main

added solution for company queries 1

Author: ks-iitjmu

9_tree_algorithms/company_queries_1.cpp

@@ -0,0 +1,69 @@
+#include <iostream>
+#include <vector>
+#include <cmath>
+#include <algorithm>
+
+using namespace std;
+
+int n, q;
+int max_log;
+vector<vector<int>> up; 
+vector<int> depth; 
+
+void dfs(int u, int p, int d, const vector<vector<int>>& child_list_ref) {
+    depth[u] = d;
+    up[u][0] = p;
+
+    for (int j = 1; j <= max_log; ++j) {
+        up[u][j] = up[up[u][j - 1]][j - 1];
+    }
+
+    for (int v : child_list_ref[u]) {
+        dfs(v, u, d + 1, child_list_ref);
+    }
+}
+
+int get_kth_ancestor(int u, int k) {
+    if (k > depth[u]) {
+        return -1;
+    }
+
+    for (int j = max_log; j >= 0; --j) {
+        if (k & (1 << j)) {
+            u = up[u][j];
+        }
+    }
+    return u;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    if (!(cin >> n >> q)) return 0;
+
+    max_log = log2(n) + 1;
+
+    up.assign(n + 1, vector<int>(max_log + 1, 0));
+    depth.assign(n + 1, 0);
+    
+    vector<vector<int>> child_list(n + 1);
+    
+    for (int i = 2; i <= n; ++i) {
+        int boss;
+        if (!(cin >> boss)) return 0;
+        child_list[boss].push_back(i);
+    }
+    
+    up[1][0] = 0; 
+    
+    dfs(1, 0, 0, child_list);
+
+    for (int i = 0; i < q; ++i) {
+        int x, k;
+        if (!(cin >> x >> k)) return 0;
+        cout << get_kth_ancestor(x, k) << "\n";
+    }
+
+    return 0;
+}