USACO Section 2.4: Bessie Come Home

/*
ID: yingzho1
LANG: C++
TASK: comehome
*/
#include <iostream>
#include <fstream>
#include <string>
#include <map>
#include <vector>
#include <set>
#include <algorithm>
#include <stdio.h>
#include <queue>
#include <cstring>
#include <cmath>
#include <list>

using namespace std;
#define inf 10000000

ifstream fin("comehome.in");
ofstream fout("comehome.out");

int N;
struct edge {
char s, d;
int e;
edge(int a, int b, int c) : s(a), d(b), e(c) { }
edge() : s(0), d(0), e(0) { }
};
map<char, int> dis;
int edgenum = 0;

int main()
{
fin >> N;
vector<edge> path(2*N);

for (int i = 0; i < N; i++) {
char s, d;
int e;
fin >> s >> d >> e;
path[edgenum].s = s;
path[edgenum].d = d;
path[edgenum++].e = e;
path[edgenum].s = d;
path[edgenum].d = s;
path[edgenum++].e = e;
}
//for (int i = 0; i < edgenum; i++) {
//cout << "s: " << path[i].s << ", d: " << path[i].d << ", e: " << path[i].e << endl;
//}
for (char i = 'a'; i <= 'z'; i++) dis[i] = inf;
for (char i = 'A'; i <= 'Z'; i++) dis[i] = inf;
dis['Z'] = 0;
bool flag;
for (int i = 0; i < edgenum; i++) {
flag = false;
for (int j = 0; j < edgenum; j++) {
if (dis[path[j].d] > dis[path[j].s]+path[j].e) {
dis[path[j].d] = dis[path[j].s]+path[j].e;
flag = true;
//cout << "dis[" << path[j].d << "]: " << dis[path[j].d] << endl;
}
}
if (!flag) break;
}
int min_path = inf;
char min_index;
for (int i = 0; i < edgenum; i++) {
if (path[i].s >= 'A' && path[i].s < 'Z' && min_path > dis[path[i].s]) {
min_path = min(min_path, dis[path[i].s]);
//cout << path[i].s << "'s dis: " << dis[path[i].s] << endl;
min_index = path[i].s;
}
}
fout <<  min_index << " " << min_path << endl;

return 0;
}