Uva-10986(Dijkstra)

#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> pii;

int arrDis[20010];
vector<pii> graph[20010];


void ans(int st)
{
    arrDis[st] = 0;
    priority_queue< pii,vector<pii>,greater<pii> > pQ;
    pQ.push(make_pair(0,st));
    while(!pQ.empty())
    {
        pii temp = pQ.top();
        int val = temp.first,curPos = temp.second;
        pQ.pop();
        if(arrDis[curPos]<val) continue;
        int sz = graph[curPos].size();
        for(int i = 0; i<sz; i++)
        {
            int nxPos = graph[curPos][i].first;
            int nxVal = graph[curPos][i].second;
            if(arrDis[nxPos]>(nxVal+val))
            {
                arrDis[nxPos] = nxVal+val;
                pQ.push(make_pair(arrDis[nxPos],nxPos));
            }
        }
    }
}

void clr()
{
    for(int i = 0; i<20010; i++)
    {
        arrDis[i] = INT_MAX;
    }
    for(int i = 0; i<20010; i++)
    {
        graph[i].clear();
    }
}
int main()
{
    int test;
    scanf("%d",&test);
    for(int i = 1; i<=test; i++)
    {
        clr();
        int node,edge,from,to;
        scanf("%d%d%d%d",&node,&edge,&from,&to);
        for(int j = 1; j<=edge; j++)
        {
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            graph[a].push_back(make_pair(b,c));
            graph[b].push_back(make_pair(a,c));
        }

        ans(from);
        if(arrDis[to] != INT_MAX)printf("Case #%d: %d\n",i,arrDis[to]);
        else printf("Case #%d: unreachable\n",i);
    }
    return 0;
}