add template and example of binary fitting

binary-lifting/tree-binary-lifting.cpp

@@ -0,0 +1,40 @@
+/*
+    Search for the Kth Ancestor of a Tree Node
+*/
+#include <vector>
+#include <bit>
+#include <bitset>
+#include <cstdint>
+
+class TreeAncestor {
+private:
+    std::vector<std::vector<int>> predecessor;
+
+public:
+    TreeAncestor(int n, std::vector<int>& parent) {
+        int m = bit_width((unsigned)n);
+        predecessor.resize(n, std::vector<int>(m, -1));
+        for (int i = 0; i < n; i++) {
+            predecessor[i][0] = parent[i];
+        }
+        for (int i = 1; i < m; i++) {
+            for (int x = 0; x < n; x++) {
+                if (int p = predecessor[x][i - 1]; p != -1) {
+                    predecessor[x][i] = predecessor[p][i - 1];
+                }
+            }
+        }
+    }
+
+    int getKthAncestor(int node, int k) {
+        // for (int i = 0; i < bit_width((unsigned)k) && node != -1; i++) {
+        //    if (k >> i & 1) {
+        //        node = predecessor[node][i];
+        //    }
+        // }
+        for (; k && node != -1; k &= k - 1) {
+            node = predecessor[node][countr_zero(unsigned(k))];
+        }
+        return node;
+    }
+};