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package leetcode.tree;

/*

* 根据前序遍历、中序遍历构造二叉树

* */

public class leetcode105 {

public TreeNode buildTree(int[] preorder, int[] inorder) {

if(preorder.length==0||inorder.length==0) return null;

return buildSubTree(preorder,inorder,0,0,inorder.length-1);

}

public TreeNode buildSubTree(int[] preorder, int[] inorder,int preindex,int start,int end) {

if(preindex > preorder.length - 1||start>end) return null;

TreeNode root=new TreeNode(preorder[preindex]); //构建根节点

for(int i=start;i<=end;i++){

if(inorder[i]==preorder[preindex]){

root.right=buildSubTree(preorder,inorder,preindex+i+1-start,i+1,end); //构建右子树,

root.left=buildSubTree(preorder,inorder,preindex+1,start,i-1); //构建左子树,左子树的根节点就在其父亲节点的下一个

break;

}

}

return root;

}

}