Solution.java

class Solution {
    private List<Integer>[] g;
    private boolean[] vis;
    private boolean[] has;
    private int[] nums;

    public int[] smallestMissingValueSubtree(int[] parents, int[] nums) {
        int n = nums.length;
        this.nums = nums;
        g = new List[n];
        vis = new boolean[n];
        has = new boolean[n + 2];
        Arrays.setAll(g, i -> new ArrayList<>());
        int idx = -1;
        for (int i = 0; i < n; ++i) {
            if (i > 0) {
                g[parents[i]].add(i);
            }
            if (nums[i] == 1) {
                idx = i;
            }
        }
        int[] ans = new int[n];
        Arrays.fill(ans, 1);
        if (idx == -1) {
            return ans;
        }
        for (int i = 2; idx != -1; idx = parents[idx]) {
            dfs(idx);
            while (has[i]) {
                ++i;
            }
            ans[idx] = i;
        }
        return ans;
    }

    private void dfs(int i) {
        if (vis[i]) {
            return;
        }
        vis[i] = true;
        if (nums[i] < has.length) {
            has[nums[i]] = true;
        }
        for (int j : g[i]) {
            dfs(j);
        }
    }
}