合法二叉树后序遍历序列

转载请注明作者与出处：franciscolv http://www.cnblogs.com/franciscolv/archive/2011/11/20/2255838.html

package SortSet;

/**
 * 判断输入数组是否为合格的二叉搜索树后续遍历结果
 * 
 * @author franciscolv
 * 
 */
public class VerifyPosOrder {

    public static void main(String[] args) {
        int[] a = { 2, 3, 9, 11, 10, 8 };
        System.out.println(verifyPosOrder(a, 0, a.length -1));
    }

    public static boolean verifyPosOrder(int[] a, int s, int e) {
        if (a == null || s > e)
            return false;
        if (s == e)
            return true;
        int root = a[e];
        int i = s;
        for (; i < e; i++)
            if (a[i] > root)
                break;
        for (int j = i + 1; j < e; j++)
            if (a[j] < root)
                return false;
        boolean left = true, right = true;
        if (i > 0)
            left = verifyPosOrder(a, s, i - 1);
        if (i < e)
            right = verifyPosOrder(a, i, e - 1);
        return left && right;

    }
}