剑指offer33_二叉搜索树的后序遍历序列(java)

二叉搜索树的后序遍历序列

递归地判断左右区间是否满足二叉搜索树的特征.

public class Solution {
    public boolean VerifySquenceOfBST(int [] sequence) {
        if(sequence == null || sequence.length == 0) return false;
        return help(sequence, 0, sequence.length-1);
    }
    
    // 划分序列的左右子区间，判断左右区间是否满足条件，递归的判断左右子区间的子区间..
    boolean help(int[] sequence, int i,int j){
        boolean flag  = true;
        if(i >= j) return true;
        int p = i;
        while(sequence[p] < sequence[j]) p++;
        int m = p;
        while(sequence[p] > sequence[j]) p++;
        if(p != j) flag = false;
        return flag && help(sequence, i, m-1) && help(sequence, m, j-1);
    }
}