1483. Kth Ancestor of a Tree Node (Leetcode)

class TreeAncestor {
public:
    vector<vector<int>> ancestor;
    TreeAncestor(int n, vector<int>& parent) {
        int logN = log2(n) + 1;
        ancestor.resize(n, vector<int>(logN, -1));
        for(int j = 0; j < logN; j++) {
            for(int i = 1; i < n; i++) {
                if(j != 0) {
                    if(ancestor[i][j - 1] != -1)
                    ancestor[i][j] = ancestor[ancestor[i][j - 1]][j - 1];
                }
                else
                ancestor[i][j] = parent[i];
            }
        }
    }
    
    int getKthAncestor(int node, int k) {
        int answer = node;
        for(int i = log2(k); i >= 0; i--) {
            if(k & (1 << i)) {
                answer = ancestor[answer][i];
                if(answer == -1) return -1;
            }
        }
        return answer;
    }
};