Help me in solving TNEIGHBOUR problem

help
,
1

My issue

I use an adjacency list to store the tree structure. Using depth first search I search for the node v in question. Upon match I check whether this was the root node or not. Counting all direct children plus 1 (has a parent node) or 0 (has no parent node) gives me the final result (number of neighbors). This works fine against the given example but fails apparently in my submission. Any help is highly appreciated. The special case of no node v found results in 0. The call stack should not get exhausted if the used compiler applies tail call elimination and no such error has been given.

My code

#include <bits/stdc++.h>
using namespace std;

static vector<int> tree[100005];

static size_t dfs(const int u, const int v) {
    if (u == v) {
        // node in question
        if (u == 1) {
            // root node
            return tree[u].size();
        }
        // inner node
        return 1 + tree[u].size();
    } else for (const int i : tree[u]) {
        // some node
        return dfs(i, v);
    }
    // node v not found
    return 0;
}

int main() {
	int n, v;
	cin >> n >> v;
	for (int i = 1; i < n; i++) {
	    int u, v;
	    cin >> u >> v;
	    tree[u].push_back(v);
	}
	cout << dfs(1, v) << endl;
}

Learning course: Trees and Binary trees
Problem Link: Neighbours of node Practice Problem in Trees and Binary trees - CodeChef

2

Nevermind. The focus was on the “undirected” property. I missed the point that more routes could lead to the node in question.

3

@dstarke
plzz refer my c++ code for better understanding of the logic

#include <bits/stdc++.h>
using namespace std;

int main() {
	// your code goes here
	
	int n;
	cin>>n;
	n--;
	int node;
	cin>>node;
	map<int,int> mp;
	while(n--)
	{
	    int u,v;
	    cin>>u>>v;
	    mp[u]++;
	    mp[v]++;
	}
	cout<<mp[node];
	return 0;
}
4

Thank you, but I have already solved it without the use of any data storage.