Update kth-ancestor-of-a-tree-node.cpp

Author: kamyu104

C++/kth-ancestor-of-a-tree-node.cpp

@@ -7,14 +7,14 @@ class TreeAncestor {
 public:
     TreeAncestor(int n, vector<int>& parent) {
         for (const auto& p : parent) {
-            parent_.emplace_back(vector<int>(1, p));
+            parent_.emplace_back(vector<int>(p != -1, p));
         }
         for (int i = 0, max_depth = 1; i < max_depth; ++i) {
             for (auto& p : parent_) {
-                if (!(i < p.size() && p[i] != -1)) {
+                if (!(i < p.size() && i < parent_[p[i]].size())) {
                     continue;
                 }
-                p.emplace_back((i < parent_[p[i]].size()) ? parent_[p[i]][i] : -1);
+                p.emplace_back(parent_[p[i]][i]);
                 if (p.size() > max_depth) {
                     max_depth = p.size();
                 }
@@ -25,7 +25,7 @@ class TreeAncestor {
     int getKthAncestor(int node, int k) {
         for (; k; k -= k & ~(k - 1)) {
             int i = __builtin_ctz(k & ~(k - 1));
-            if (!(i < parent_[node].size() && parent_[node][i] != -1)) {
+            if (!(i < parent_[node].size())) {
                 return -1;
             }
             node = parent_[node][i];