【leetcode】1443. Minimum Time to Collect All Apples in a Tree

用递归

提交代码

class Solution {
    public int minTime(int n, int[][] edges, List<Boolean> hasApple) {
        TreeNode[] nodes=new TreeNode[n];
        
        for(int i=0;i<n;i++) 
        	nodes[i]=new TreeNode(i);
        
        for(int[] e:edges) {
        		nodes[e[0]].next.add(nodes[e[1]]);
        }
        
        int res=0;
        for(TreeNode node : nodes[0].next) {
        	res+=countPath(node,hasApple);
        }
        return res;
    }
    
    private int countPath(TreeNode root, List<Boolean> hasApple) {
        int res=0;
    	if(root==null)	return 0;
    	for(TreeNode node: root.next) {
    		res+=countPath(node, hasApple);
    	}
    	if(res==0&&hasApple.get(root.val))
    		return 2;
    	else if(res==0&&!hasApple.get(root.val))
    		return 0;
    	return res+2;
    }
}

class TreeNode {
    int val;
    List<TreeNode> next=new ArrayList<>();
    TreeNode(int x) { val = x; }
}

运行结果