Java实现二叉树

public class Tree2Bef { 
private StringBuffer bef=new StringBuffer(); 

//传入中序遍历和后序遍历,返回前序遍历字串 
public String getBef(String mid, String beh) { 
//若节点存在则向bef中添加该节点,继续查询该节点的左子树和右子树 
if (root(mid, beh) != -1) { 
int rootindex=root(mid, beh); 
char root=mid.charAt(rootindex); 
bef.append(root); 
System.out.println(bef.toString()); 
String mleft, mright; 
mleft = mid.substring(0,rootindex); 
mright = mid.substring(rootindex+1); 
getBef(mleft,beh); 
getBef(mright,beh); 
} 
//所有节点查询完毕,返回前序遍历值 
return bef.toString(); 

} 

//从中序遍历中根据后序遍历查找节点索引值index 
private int root(String mid, String beh) { 
char[] midc = mid.toCharArray(); 
char[] behc = beh.toCharArray(); 
for (int i = behc.length-1; i > -1; i--) { 
for (int j = 0; j < midc.length; j++) { 
if (behc[i] == midc[j]) 
return j; 
} 
} 
return -1; 
} 

public static void main(String[] args) { 
Tree2Bef tree=new Tree2Bef(); 
String mid="84925163A7B"; 
String bef="894526AB731"; 
System.out.println(tree.getBef(mid,bef)); 
} 
}