【其他】根据前序和中序构建后序

package top.actim.test09;

public class Solution {
	/**
	 * 
	 * @param preorderData long长整型一维数组
	 * @param inorderData  long长整型一维数组
	 * @return long长整型一维数组
	 */
	public long[] buildPostOrder(long[] preorderData, long[] inorderData) {
		// write code here
		long[] ans = new long[preorderData.length];

		build(ans, preorderData, inorderData, 0, 0, 0, preorderData.length);

		return ans;
	}

	void build(long[] ans, long[] pre, long[] ino, int a, int p, int o, int len) {

		long tar = pre[p];
		ans[a + len - 1] = tar;

		if (len == 1) {
			return;
		}

		int mid = 0;
		for (int i = o; i < o + len; i++) {
			if (ino[i] == tar) {
				mid = i;
			}
		}

		int llen = mid - o;
		int rlen = len - llen - 1;

		build(ans, pre, ino, a, p + 1, o, llen);
		build(ans, pre, ino, a + llen, p + llen + 1, o + llen + 1, rlen);

	}

	public static void main(String[] args) {
		long[] pre = { 1, 2, 3 };
		long[] ino = { 2, 1, 3 };
		long[] ans = new Solution().buildPostOrder(pre, ino);

		for (int i = 0; i < ans.length; i++) {
			System.out.println(ans[i]);
		}
	}

}