Question

我一直在尝试解决SPOJ上的SHPATH问题，这只是Djikstra算法的直接实现。

http://www.spoj.com/problems/TSHPATH/

#include <iostream>
#include <map>
#include <queue>
using namespace std;

class Graph{
    public:
        vector< pair<int,int> > adjList[10001];
        void addEdge(int city_index, int neighbor, int dist){
            adjList[city_index].push_back(make_pair(neighbor,dist));
        }
};

struct comp{
    bool operator()(const pair<int,int>& a, const pair<int,int>& b){
        return a.second > b.second;
    }
};

int dijkstra(Graph graph, int n, int source, int dest){
    priority_queue< pair<int,int>, vector< pair<int,int> >, comp> pqi;
    map<int,int> visited;
    int curr_dist;
    vector< pair<int,int> > curr;
    //Start from the source
    pqi.push(make_pair(source,0));
    while(visited.size() < n && pqi.empty == false){
        //Check if it is already visited, If already visited, then ignore
        while(visited.find(pqi.top().first) != visited.end()){
            pqi.pop();
        }
        curr = graph.adjList[pqi.top().first];
        curr_dist = pqi.top().second;
        //Mark it as visited
        visited[pqi.top().first] = curr_dist;
        pqi.pop();
        //Visit all the neighbors
        for(int j=0; j<curr.size(); j++){
            //If not already visited, then visit it
            if(visited.find(curr[j].first) == visited.end()){
                pqi.push(make_pair(curr[j].first,curr_dist+curr[j].second));
            }
        }
    }
    return visited[dest];
}

int main() {
    int t,n,neighbors,a,b,queries;
    string city1,city2;
    string city_name;
    string emptyline;
    map<string,int> city_index;
    cin>>t;
    for(int testcase=0; testcase<t; testcase++){
        Graph graph = Graph();
        cin>>n;
        for(int city=1; city<=n; city++){
            cin>>city_name;
            city_index[city_name] = city;
            cin>>neighbors;
            for(int neighbor=0; neighbor<neighbors; neighbor++){
                cin>>a>>b;
                graph.addEdge(city,a,b);
            }
        }
        cin>>queries;
        for(int query=0; query<queries; query++){
            cin>>city1>>city2;
            cout<<dijkstra(graph,n,city_index[city1],city_index[city2])<<endl;
        }
        getline(cin,emptyline);
    }
    return 0;
}

我已经针对来自http://spojtoolkit.com/test/SHPATH

的大量测试用例进行了测试

它给出了所有测试用例的正确答案。似乎无法弄清楚，在哪里发生了分段错误，因为没有数组索引超出界限且没有野性指针等。

Answer 1

在函数djikstra()中，此行已被修改：

while(visited.size() < n && pqi.empty() == false)

现在，对于所有测试用例，解决方案运行正常。

SPOJ SHPATH - SIGSEV错误

1 个答案: