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With respect to this problem : 2050G - Tree Destruction

Using vector of vector, compiled successfully and giving correct output

int n;
        cin>>n;

        vector<vector<int>> g(n);
        vector<int> deg(n);
        for(int i=0, u, v; i<n-1; i++){
            cin>>u>>v;
            --u, --v;
            g[u].pb(v);
            g[v].pb(u);
            ++deg[u], ++deg[v];
        }

        int ans = 1;
        auto dfs = [&](auto self, int v, int p = -1) -> int {
            int mx1 = 0, mx2 = 0;
            for(auto &c : g[v]){
                if(c == p) continue;
                int res = self(self,c,v);
                if(res > mx1) mx2 = mx1, mx1 = res;
                else mx2 = max(mx2, res);
            }
            ans = max(ans, mx1+mx2-(mx1>0)-(mx2>0)+deg[v]);
            return (mx1-(mx1>0)+deg[v]-1);
        };

        dfs(dfs,0);
        cout<<ans<<nl;

But when trying the same with array of vectors, it doesn't compile

int n;
        cin>>n;

        vector<int> g[n];
        vector<int> deg(n);
        for(int i=0, u, v; i<n-1; i++){
            cin>>u>>v;
            --u, --v;
            g[u].pb(v);
            g[v].pb(u);
            ++deg[u], ++deg[v];
        }

        int ans = 1;
        auto dfs = [&](auto self, int v, int p = -1) -> int {
            int mx1 = 0, mx2 = 0;
            for(auto &c : g[v]){
                if(c == p) continue;
                int res = self(self,c,v);
                if(res > mx1) mx2 = mx1, mx1 = res;
                else mx2 = max(mx2, res);
            }
            ans = max(ans, mx1+mx2-(mx1>0)-(mx2>0)+deg[v]);
            return (mx1-(mx1>0)+deg[v]-1);
        };

        dfs(dfs,0);
        cout<<ans<<nl;

Error by compiler -> error: use of deleted function 'main()::<lambda(auto:28, int, int)>::~<lambda>()' <lambda(auto:28, int, int)>::~<lambda>()' is implicitly deleted because the default definition would be ill-formed:

I want to know why this is happening. Can someone please tell me the reason behind this unknown behavior of lambda function ?

Rev.	By	When	Δ	Comment
en5	Intuition2.0	2024-12-07 01:43:25	4
en4	Intuition2.0	2024-12-07 01:39:28	41
en3	Intuition2.0	2024-12-07 01:32:43	223
en2	Intuition2.0	2024-12-07 01:28:22	22
en1	Intuition2.0	2024-12-07 01:27:03	2185	Initial revision (published)

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en5