优化BFS的实施

我正在学习Graph的基础知识，并从
开始解决问题https://www.hackerrank.com/challenges/bfsshortreach.代码运行良好，但我得到了一个测试用例的TLE。我把cin/cout改成了printf/scanf，希望它能被接受，但没有成功。到目前为止，我的代码是

#include <iostream>
#include <queue>
#include <climits>
#include <stdio.h>
#include <queue>
#include <list>
#include <vector>
struct Graph
{
    int size;
    std::list<int> *adj;
};
Graph* createGraph(int size)
{
    Graph *graph = new Graph();
    graph->size = size;
    graph->adj = new std::list<int>[size];
    return graph;
}
void addEdge(Graph *graph, int source, int dest)
{
    graph->adj[source].push_back(dest);
    graph->adj[dest].push_back(source);
}
void printGraph(Graph *graph)
{
    for (int i = 0; i < graph->size; ++i)
    {
        for(std::list<int>::iterator it = graph->adj[i].begin(); it!= graph->adj[i].end(); ++it)
          {
            std::cout<<*it<<' ';
          }
          std::cout<<std::endl;
    }
}
void BFS(Graph *graph, int src)
{
    std::queue <int> nodes;
    std::vector<bool> v(graph->size,false);
    std::vector<int> distance(graph->size, INT_MAX);
    v[src] = true;
    distance[src] = 0;
    nodes.push(src);
    std::list<int>::iterator it;
    while(!nodes.empty())
    {
        int temp = nodes.front();
        v[temp] = true;
        nodes.pop();
        for(it = graph->adj[temp].begin(); it!= graph->adj[temp].end(); ++it)
          {
            if(!v[*it])
            {
                nodes.push(*it);
                int current = distance[temp] != INT_MAX? distance[temp] : 0;
                distance[*it] = std::min(current + 6, distance[*it]);
            }
          }
    }
    for (int i = 0; i < distance.size(); ++i)
    {
        int dist = distance[i] != INT_MAX ?  distance[i] : -1;
        if(i!= src)
        {
            printf("%d ", dist);
        }
    }
        printf("n");
}
int main(int argc, char const *argv[])
{
    int T;
    scanf(" %d", &T);
    while(T--) {
        int n, m, s;
        // cin>>n>>m;m
        scanf(" %d %d", &n, &m);
        Graph *graph = createGraph(n);
        while(m--)
        {
            int x, y;
            // cin>>x>>y;
            scanf(" %d %d", &x, &y);
            addEdge(graph, x-1, y-1);
        }
        // cin>>s;
        scanf(" %d", &s);
        BFS(graph, s-1);
        // printGraph(graph);
    }
    return 0;
}

我相信CCD_ 1。并且插入边所需的时间复杂度是 O(1) 。所以AFAIK，这是我们能做的最好的事情（也许？）。我不确定这是否是存储图形的最佳方式。任何更好、更快的存储图形的方法和改进建议都将非常棒。