struct Solution;
use std::collections::HashMap;
impl Solution {
fn delete_tree_nodes(nodes: i32, parent: Vec<i32>, value: Vec<i32>) -> i32 {
let mut hm: HashMap<usize, Vec<usize>> = HashMap::new();
let n = nodes as usize;
let mut root = n;
for i in 0..n {
if parent[i] != -1 {
hm.entry(parent[i] as usize).or_default().push(i);
} else {
root = i;
}
}
let (_, size) = Self::postorder(root, &hm, &value, n);
size as i32
}
fn postorder(
i: usize,
hm: &HashMap<usize, Vec<usize>>,
value: &[i32],
n: usize,
) -> (i32, usize) {
let mut sum = value[i];
let mut size = 1;
if let Some(children) = hm.get(&i) {
for &j in children {
let child = Self::postorder(j, hm, value, n);
sum += child.0;
size += child.1;
}
}
if sum == 0 {
(0, 0)
} else {
(sum, size)
}
}
}
#[test]
fn test() {
let nodes = 7;
let parent = vec![-1, 0, 0, 1, 2, 2, 2];
let value = vec![1, -2, 4, 0, -2, -1, -1];
let res = 2;
assert_eq!(Solution::delete_tree_nodes(nodes, parent, value), res);
}