举例让抽象问题具体化:二叉搜索树的后序遍历序列
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); } }