class Solution {
    public boolean verifyPostorder(int[] postorder) {
        int n = postorder.length;
        if(n<=1) return true;
        int j = n-1;
        for(;j>=0;j--){
            if(postorder[j]<postorder[n-1]){
                break;
            }
        }
        int[] left = Arrays.copyOfRange(postorder,0,j+1);
        
 
int[] right = Arrays.copyOfRange(postorder,j+1,n-1);
        return track(postorder[n-1],left,right);
    }

    private boolean track(int root, int[] left, int[] right) { 
        if(left.length>0){
            for (int value : left) {
                if (value > root) {
                    return
 
 false;
                }
            }
        }
        if(right.length>0){
            for (int value : right) {
                if (value < root) {
                    return false;
                }
            }
        }
        return verifyPostorder(left) && verifyPostorder(right);
    }
}
 

遞迴。

單調棧的想法還不會實現。