/Duyệt cây nhị phân

      #include <iostream>
        #include <vector>
        using namespace std;
        
        #define MAX 50001
        
        int n;
        int node[MAX];
        int c[MAX];
        
        vector <int> arr;
        
        void postOrder(int preOLeft, int preORight, int inOLeft, int inORight) {
          if (preOLeft > preORight) return;
        
          int rootNodeIndex = preOLeft;
        
          arr.push_back(node[rootNodeIndex]);
        
          if (preOLeft == preORight) return;
          else {
            int numOfNodeToTheLeft = c[node[rootNodeIndex]] - inOLeft;
            int numOfNodeToTheRight = inORight - c[node[rootNodeIndex]];
            postOrder(preOLeft + numOfNodeToTheLeft + 1, preORight, c[node[rootNodeIndex]] + 1, inORight);
            postOrder(preOLeft + 1, preORight - numOfNodeToTheRight, inOLeft, c[node[rootNodeIndex]] - 1);
          }
        
        }
        
        int main() {
          cin >> n;
        
          for (int i = 1; i <= n; i++) cin >> node[i];
          for (int i = 1; i <= n; i++) {
            int x;
            cin >> x;
            c[x] = i;
          }
        
          postOrder(1, n, 1, n);
        
          for (int i = arr.size() - 1; i >= 0; i--) cout << arr[i] << " ";
          cout << endl;
        
          return 0;
        }