剑指offer-面试题6：重建二叉树

题目

解

public static TreeNode buildTree(int[] preOrder,
int start,int[] inOrder,int end,int length){

//参数验证
if(preOrder==null||preOrder.length==0
||inOrder==null||inOrder.length==0||length<=0){

return null;

}

//建立子树根节点
int value=preOrder[start];
TreeNode root=new TreeNode(value);

//递归终止条件：子树只有一个节点
if(length==1){
return root;
}

//分拆子树的左子树和右子树
int i=0;
while(i<length){
if(value==inOrder[end-i]){
break;
}
i++;
}

//建立子树的左子树
root.left=buildTree(preOrder,start+1,inOrder,end-1-i,length-1-i);
root.right=buildTree(preOrder,start+length-i,inOrder,end,i);

return root;

}