[프로그래머스][Level3] 가장 먼 노드 c++

https://programmers.co.kr/learn/courses/30/lessons/49189 

프로그래머스

 

풀이 과정

이 문제는 다익스트라의 기본 문제이다.  
다익스트라 알고리즘을 활용하여 dist 값을 찾아낸 뒤,  
가장 큰 값을 찾아 그 값과 일치하는 개수를 세면 된다.

 

#include <string>
#include <vector>
#include <queue>

using namespace std;

const int INF = 1e9;
vector<int> dist;
vector<pair<int, int>> edge[20001];

priority_queue<pair<int, int>> pq;

void dijkstra(int n){
    dist.resize(n + 1, INF);
    dist[1] = 0;
    pq.push({0, 1}); // 가중치, 정점

    while(!pq.empty()){
        int cost = -pq.top().first;
        int now = pq.top().second;
        pq.pop();

        if(dist[now] < cost) continue;
        for(int i = 0; i < edge[now].size(); i++){
            int next = edge[now][i].first;
            int nextcost = edge[now][i].second;

            if(dist[next] > dist[now] + nextcost){
                dist[next] = dist[now] + nextcost;
                pq.push({-dist[next], next});
            }
        }
    }
}

int solution(int n, vector<vector<int>> vertex) {
    int answer = 0;

    for(int i = 0; i < vertex.size(); i++){
        edge[vertex[i][0]].push_back({vertex[i][1], 1}); // 도착 정점, 가중치
        edge[vertex[i][1]].push_back({vertex[i][0], 1});
    }
    dijkstra(n);

    int max = 0;
    for(int i = 1; i <= n; i++){
        if(max < dist[i]) max = dist[i];
    }
    for(int i = 1; i <= n; i++){
        if(max == dist[i]) answer++;
    }
    return answer;
}