ConstructBinaryTreefromPreorderandInorderTraversal

//Given preorder and inorder traversal of a tree, construct the binary tree.
public class ConstructBinaryTreefromPreorderandInorderTraversal {


public static void main(String[] args) {
// TODO Auto-generated method stub


}
public TreeNode buildTree(int[] preorder, int[] inorder) {
if(preorder.length==0)
return null;
TreeNode root=new TreeNode(preorder[0]);
int i;
int count=inorder.length;
for(i=0;i<count;i++){
if(inorder[i]==preorder[0])
break;
}
TreeNode left=create(preorder,1,i,inorder,0,i-1);
TreeNode right=create(preorder,i+1,count-1,inorder,i+1,count-1);
root.left=left;
root.right=right;
return root;
}
private TreeNode create(int[] preorder, int s, int e, int[] inorder, int si, int ei) {
// TODO Auto-generated method stub
//没有元素了
if(s>e)
return null;
TreeNode root=new TreeNode(preorder[s]);
int i;
for(i=si;i<=ei;i++){
if(inorder[i]==preorder[s])
break;
}
TreeNode left=create(preorder,s+1,s+1+i-1-si,inorder,si,i-1);
TreeNode right=create(preorder,e-ei+i+1,e,inorder,i+1,ei);
root.left=left;
root.right=right;
return root;
}


}