重建二叉树

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
private List<Integer> postTree;

private boolean rebuildTree(int[] preTree, int preStart, int preEnd, int[] inTree, int inStart, int inEnd) {
if (preEnd - preStart != inEnd - inStart) { // 剪枝
return false;
}

if (preEnd < preStart) { // 递归出口
return true;
}

// 在中序遍历结果中查找根节点的位置
int rootPosition = -1;
for (int i = inStart; i <= inEnd; ++i) {
if (preTree[preStart] == inTree[i]) {
rootPosition = i;
break;
}
}

// 中序遍历中找不到根节点，则无法重建二叉树
if (-1 == rootPosition) { // 剪枝
return false;
}

int leftSize = rootPosition - inStart;
boolean result = rebuildTree(preTree, preStart + 1, preStart + leftSize, inTree, inStart, rootPosition - 1) &&
rebuildTree(preTree, preStart + leftSize + 1, preEnd, inTree, rootPosition + 1, inEnd);

postTree.add(preTree[preStart]);
return result;
}

public static void main(String[] args) {
int n = 0;
Scanner cin = new Scanner(System.in);
Main M = new Main();
while (cin.hasNext()) {
n = cin.nextInt();
int[] preTree = new int
;
for (int i = 0; i < n; ++i) {
preTree[i] = cin.nextInt();
}

int[] inTree = new int
;
for (int i = 0; i < n; ++i) {
inTree[i] = cin.nextInt();
}

M.postTree = new ArrayList<Integer>(n);
boolean ret = M.rebuildTree(preTree, 0, n - 1, inTree, 0, n - 1);
if (ret) {
for (int i = 0; i < n; ++i) {
System.out.print(M.postTree.get(i) + " ");
}
System.out.println();

} else {
System.out.println("No");
}
} // while

cin.close();
} // main
} // class

/**************************************************************
Problem: 1385
User: buptxxz
Language: Java
Result: Accepted
Time:310 ms
Memory:19100 kb
****************************************************************/