举例让抽象问题具体化：二叉搜索树的后序遍历序列

Posted 2020-08-04 SaraMorning

输入一个整数数组，判断该数组是不是某二叉搜索树的后序遍历的结果。如果是则输出Yes,否则输出No。假设输入的数组的任意两个数字都互不相同。

public class Solution {
    public boolean VerifySquenceOfBST(int [] sequence) {
        if (sequence.length == 0) {
            return false;
        }
        return judge(sequence, 0, sequence.length-1);
    }

    public boolean judge(int[] sequence, int left, int right) {
        if (left >= right)
            return true;
        int i = right;
        while (i > left && sequence[i - 1] > sequence[right])
            --i;
        for (int j = i - 1; j >= left; --j) {
            if (sequence[j] > sequence[right]) {
                return false;
            }
        }
        return judge(sequence, left, i - 1) && judge(sequence, i, right - 1);

    }
}