CONSTRUCT A BINARY TREE FROM PREORDER AND INORDER TRAVERSAL.cpp

class Solution
{
public:
     TreeNode *solve(vector<int> &preorder, vector<int> &inorder, int start, int end, int &idx)
     {
          if (start > end)
               return NULL;

          int rootVal = preorder[idx];
          int i = start;
          for (; i <= end; i++)
          {
               if (inorder[i] == rootVal)
                    break;
          }
          idx++;
          TreeNode *root = new TreeNode(rootVal);
          root->left = solve(preorder, inorder, start, i - 1, idx);
          root->right = solve(preorder, inorder, i + 1, end, idx);

          return root;
     }

     TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder)
     {
          int n = preorder.size();
          int idx = 0;
          return solve(preorder, inorder, 0, n - 1, idx);
     }
};

// LEETCODE PROBLEM - 105