[数据结构与算法]51Nod - 2602_树的直径

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//
#include<iostream>
#include<algorithm>
#include<vector>        //
using namespace std;

// 1<=n<=100000
const int MAXN=1e5+6;

vector<int> e[MAXN];
int d_all[MAXN];
int cnt_all[MAXN];

void dfs( int son,int father,int d,int cnt )
{
    int i;
    d_all[son]=d;           // 莫 +1
    cnt_all[son]=cnt;       // 

    for( i=0;i<e[son].size();i++ )
    {
        if( e[son][i]!=father )
        {
            dfs( e[son][i], son, d+1, cnt+1 );
        }
    }
}

int main()
{
    int n,a,b,i,maxa,maxb;

    scanf("%d",&n);

    for( i=0;i<n-1;i++ )
    {
        scanf("%d%d",&a,&b);
        e[a].push_back( b );
        e[b].push_back( a );
    }
    dfs( 1,-1,0,0 );

    maxa=1;
    for( i=1;i<=n;i++ )
    {
        if( d_all[i]>d_all[maxa] ) maxa=i;
    }
    dfs( maxa,-1,0,0 );

    maxb=1;
    for( i=1;i<=n;i++ )
    {
        if( d_all[i]>d_all[maxb] ) maxb=i;
    }
    printf("%d\n",cnt_all[maxb]);

    return 0;
}

//
find:
01 带上 vector 头文件
02 到底 +1 否？