根据中序和前序遍历结果构建二叉树

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public class Main1 { 
    public static class TreeNode{ 
    int val; TreeNode left; TreeNode right; TreeNode(int x) { 
    val=x; } } public static void main(String[] args) { 
    int[] in=new int[] { 
   4,7,2,1,5,3}; int[] pre=new int[] { 
   1,2,4,7,3,5}; TreeNode root=build(in,0,in.length-1,pre,0,pre.length-1); bianli(root); } public static void bianli(TreeNode root) { 
    if(root==null) { 
    return ; } bianli(root.left); System.out.println(root.val); bianli(root.right); } public static TreeNode build(int[] in,int inleft,int inright,int[] pre, int preleft,int preright) { 
    if(inleft>inright||preleft>preright) { 
    return null; } TreeNode root=new TreeNode(pre[preleft]); for(int i=inleft;i<=inright;i++) { 
    if(in[i]==pre[preleft]) { 
    root.left=build(in,inleft,i-1,pre,preleft+1,preleft+i-inleft); root.right=build(in,i+1,inright,pre,preleft+i-inleft+1,preright); } } return root; } }