题目描述
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。
递归判断左右子树是否满足二叉搜索树的条件，即左子树都比root小，右子树都比root大。
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| public boolean VerifySquenceOfBST(int[] sequence) {
if (sequence == null || sequence.length == 0) {
return false;
}
int left = 0, root = sequence[sequence.length - 1];
for (; left < sequence.length - 1; left++) {
if (sequence[left] > root) {
break;
}
}
for (int i = left; i < sequence.length - 1; i++) {
if (sequence[i] < root) {
return false;
}
}
boolean leftOk = true;
if (left > 2) {
leftOk = VerifySquenceOfBST(Arrays.copyOf(sequence, left));
}
boolean rightOk = true;
if (sequence.length - 1 - left > 2) {
rightOk = VerifySquenceOfBST(Arrays.copyOfRange(sequence, left, sequence.length - 1));
}
return leftOk && rightOk;
}
|