蓝桥杯 -- 大臣的旅费

 

 

 

 路费和走的距离的关系是等差数列    cost = 11 *n  + n*(n-1)/2 

 然后用Folyd 求出所有城市之间的距离.找最大 ,特殊 n = 1 的时候 . 

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <set>
#include <cstring>
#include <stack>
#include <vector>
#include <queue>
#define Swap(a,b)  a ^= b ^= a ^= b
#define cl(a,b) memset(a,b,sizeof(a))
using namespace std ;
typedef long long LL;
const int N = 1e7+10 ;

LL gcd(LL a,LL b){return b?gcd(b,a%b):a;}
LL lcm(LL a,LL b){return a/gcd(a,b)*b;}
const int MAX = 1005;
const int inf = 0xffffff;
const LL mod = 1e9+7 ;

priority_queue<int,vector<int>,greater<int> > Q ;
// 小跟堆

int Map[MAX][MAX] ;
int vis[MAX];
int n ;

int main()
{
	ios_base::sync_with_stdio(false);
    cin.tie(NULL),cout.tie(NULL);
	int n ;
	cin >>n ;
	if(n == 1 ){
		cout<<"0"<<endl;
		return 0 ;
	}
	for(int i = 1 ; i<=n ;i++ ){
		for(int j = 1 ; j<=n ;j++){
			Map[i][j] = inf ;
			if(i == j ){
				Map[i][j] = 0;
			}
		}
	}
	
	for(int i = 1 ; i<n ; i++){
		int u , v ,w ;
		cin >> u >> v>>w ;
		Map[u][v] = w ;
		Map[v][u] = w ;
	}

	int maxx = -inf;
	for(int k = 1 ; k<=n ;k++){

		for(int i = 1 ; i<=n ; i++){
			for(int j = 1 ; j<=n ; j++ ){

				if(Map[i][j] > Map[i][k] + Map[k][j]  && Map[i][k]!=inf&& Map[k][j]!=inf){
				   Map[j][i] = Map[i][j] = Map[i][k] + Map[k][j] ;
				}

			}
		}
	}
	
	for(int i = 1 ; i<=n ; i++ ){
		for(int j= 1 ; j<=n ;j++){
			if(Map[i][j]!=inf && i!=j){
				maxx = max(maxx,Map[i][j]) ;
			}
		}
	}
	
	cout<<maxx*11+ maxx*(maxx-1)/2 <<endl;
    return 0;
}