The diameter of the gym-101522b tree

gym-101522b

Test Instructions:

Give a tree, then create a new edge in the way given, and then build a layer of edges until you can build it. Ask how many hours, every one hours can build an edge, can be multi-threaded build.

Ideas:

Drawing can find the law, the worst case is that n points is a linear, then the time will be the longest, according to the linear law found that its length and time is twice times the increment, each new hour can be on the original basis to draw twice times the line, so find the longest side and then Judge 2 of the ANS can.

#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <

Queue> #include <vector> using namespace std;

const int MAXN = 5E5+10;
    struct Edge {int to,v;
int next;

}EDGE[MAXN*2];
int n;

int head[maxn],pos;
int dp[maxn][3];

int SONMAX[MAXN];
    void init () {pos = 0;
    memset (head,-1,sizeof (head));
    Memset (Dp,0,sizeof (DP));
memset (sonmax,0,sizeof (Sonmax));
    } void Add_edge (int u,int v,int val) {edge[pos].to = v;
    EDGE[POS].V = val;
    Edge[pos].next = Head[u];
    Head[u] = pos++;
    edge[pos].to = u;
    EDGE[POS].V = val;
    Edge[pos].next = Head[v];
HEAD[V] = pos++;
        } void Input () {for (int i = 2;i <= n; i++) {int A, B;
        scanf ("%d%d", &a,&b);
    Add_edge (a,b,1);
    }} void dfs1 (int u,int fa) {dp[u][0] = dp[u][1] = dp[u][2] = Sonmax[u] = 0;
        for (int i = head[u];i! =-1; i = edge[i].next) {int to = edge[i].to; if (to = = fa) continue;
        DFS1 (To,u);
            if (Dp[u][0] < dp[to][0] + edge[i].v) {Sonmax[u] = to;
            DP[U][1] = max (dp[u][0],dp[u][1]);
        Dp[u][0] = dp[to][0] + edge[i].v;   
    } else dp[u][1] = max (dp[u][1],dp[to][0] + edge[i].v);
        }} void dfs2 (int u,int fa) {for (int i = head[u];i! = 1; i = edge[i].next) {int to = edge[i].to;
        if (to = = FA) continue;
        if (sonmax[u] = = to) {dp[to][2] = max (dp[u][2],dp[u][1]) + edge[i].v;
        } else dp[to][2] = max (dp[u][2],dp[u][0]) + edge[i].v;
    DFS2 (To,u);

    }} int main (int argc, char const *argv[]) {//freopen ("In.txt", "R", stdin);
    scanf ("%d", &n);
    Init ();
    Input ();
    DFS1 (1,-1);
    DFS2 (1,-1);
    int Max = 0;
    for (int i = 1;i <= n; i++) {max = max (max,dp[i][0]+dp[i][2]);
    A long long is 2;
    int ans = 1;
        while (both < Max) {n = two*2;
    ans++;
    }if (n = = 2) ans = 0;
    printf ("%d\n", ans);
return 0; }