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package byteDance;

/**

* Created by lizeyang on 2020/5/14.

* 重建二叉树

*/

public class test24 {

//根据先序中序序列恢复二叉树

public static TreeNode test(int[] pre,int[] in){

if(pre==null||in==null||pre.length!=in.length){

return null;

}

return reBuild(pre,0,pre.length-1,in,0,in.length-1);

}

public static TreeNode reBuild(int[] pre,int preStart,int preEnd,int[] in,int inStart,int inEnd){

if(preStart>preEnd||inStart>inEnd){

return null;

}

TreeNode root = new TreeNode(pre[preStart]);

for(int i=inStart;i<=inEnd;i++){

if(in[i] == root.val){

root.left = reBuild(pre,preStart+1,preStart+i-inStart,in,inStart,i);

root.right = reBuild(pre,preStart+i-inStart+1,preEnd,in,i+1,inEnd);

}

}

return root;

}

}