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 == null || sequence.length == 0)
return false;
return IsTreeBST(sequence, 0, sequence.length-1);
}
public boolean IsTreeBST(int[] sequence, int begin,int end) {
if(begin >= end)
return true;
int i = begin;
for(; i < end; ++i)
{
if(sequence[i] > sequence[end])
break;
}
int j = i;
for(;j < end; ++j)
{
if(sequence[j] < sequence[end])
return false;
}
boolean left = true;
if(i > 0)
left = IsTreeBST(sequence, begin, i-1);
boolean right = true;
if(i < sequence.length-1)
right = IsTreeBST(sequence, i, end-1);
return left && right;
}
}