ZOJ 2326 Tangled in Cables

#include <iostream>
#include <cstdio>
#include <string>
#include <map>
#include <algorithm>
using namespace std;
const int maxn = 301;
map<string, int> sToNum;
struct edge{
int u, v;
double w;
bool operator<(const edge & rhs)const{
return w < rhs.w;
}
}es[maxn * maxn];
double len;
int id[maxn], size[maxn], n ,m;
void init(int n){
sToNum.clear();
for (int i = 1; i <= n; ++i){
id[i] = i;
size[i] = 1;
}
}
int find(int p){
return p == id[p] ? p : id[p] = find(id[p]);
}
bool uni(int p, int q){
int pq = find(p), pp = find(q);
if(pp == pq)return false;
if(size[pp] > size[pq]){
id[pq] = pp;
size[pp] += size[pq];
}else{
id[pp] = pq;
size[pq] += size[pp];
}
return true;
}
double kruskcal(int eidx){
sort(es, es + eidx);
int i = 0, j = 0;
double ans = 0;
for (; i < eidx && j < n - 1; ++i){
if(uni(es[i].u, es[i].v)){
j++;
ans += es[i].w;
}
}
if(j == n -1){
return ans;
}else{
return -1;
}
}
int main(){
while (~scanf("%lf", &len)){
int eidx = 0;
scanf("%d", &n);
init(n);
for (int i = 1; i <= n; ++i){
char name[30];
scanf("%s", name);
sToNum[name] = i;
}
scanf("%d", &m);
for (int i = 0; i < m; ++i){
char b1[30], b2[30];
double dis;
scanf("%s %s %lf", b1, b2, &dis);
int u = sToNum[b1], v = sToNum[b2];
es[eidx].u = u, es[eidx].v = v, es[eidx++].w = dis;
es[eidx].u = v, es[eidx].v = u, es[eidx++].w = dis;
}
double ans = kruskcal(eidx);
if(ans == -1){
printf("Not enough cable\n");
}else{
printf("Need %.1lf miles of cable\n",ans);
}
}
return 0;
}