codevs 1814 最长链

二次联通门 : codevs 1814 最长链

/*
    codevs 1814 最长链
    
    树形DP
    当前点(LQZ)的最大价值由他的
        左儿子(HKD) 和 右儿子(SYL)的最大价值转移而来
    
    其余细节乱搞一下就可
     
    我还是水的很开心啦..
     
*/
#include <cstdio>

#define Max 100080

inline int max (int a, int b)
{
    return a > b ? a : b;
}

void read (int &now)
{
    now = 0;
    register char word = getchar ();
    while (word > '9' || word < '0')
        word = getchar ();
    while (word >= '0' && word <= '9')
    {
        now = now * 10 + word - '0';
        word = getchar ();
    }
}

struct Tree_Type
{
    int Left_Child;
    int Right_Child;
};

Tree_Type tree[Max];

int dp[Max];
int number[Max];
int Answer;

void Dfs (int now)
{
    dp[now] = 1;
    if (tree[now].Left_Child == 0 && tree[now].Right_Child == 0)
        return ;
    if (tree[now].Left_Child)
        Dfs (tree[now].Left_Child);
    if (tree[now].Right_Child)
        Dfs (tree[now].Right_Child);
    dp[now] = max (dp[tree[now].Left_Child], dp[tree[now].Right_Child]) + 1;
    Answer = max (Answer, dp[tree[now].Left_Child] + dp[tree[now].Right_Child] + 1);
}

int N;

int main (int argc, char *argv[])
{
    read (N);
    int x, y;
    for (register int i = 1; i <= N; i++)
    {
        read (x);
        read (y);
        tree[i].Left_Child = x;
        tree[i].Right_Child = y;
    }
    Dfs (1);
    printf ("%d", Answer - 1);
    return 0;
}