POJ-1251(Jungle Roads) Kruskal

POJ-1251

#include 
#include 
#include 
#include 
using namespace std;

const int MAXN = 30;
const int INF = 0x3f3f3f3f;
int f[MAXN];

struct _Edge {
    int from, to, val;
    _Edge() {
    }
    _Edge(int _from, int _to, int _val): from(_from), to(_to), val(_val) {
    }
};
_Edge edge[MAXN*(MAXN - 1)];
int n, cnt;

bool cmp(_Edge rhs1, _Edge rhs2) {
    return rhs1.val < rhs2.val;
}
int find(int x) {
    return f[x] == -1 ? x : find(f[x]);
}

int kruskal() {
    for(int i = 0; i < MAXN; ++i) f[i] = -1;
    int res = 0;
    int p = 0;
    for(int i = 0; i < cnt; ++i) {
        int x = find(edge[i].from);
        int y = find(edge[i].to);
        int val = edge[i].val;

        if(x != y) {
            f[x] = y;
            res += val;
            p ++;
        }
        if(p == n - 1) break;
    }
    if(p < n - 1) return -1;
    else return res;
}

void addEdge(int u, int v, int w) {
    edge[cnt].from = u;
    edge[cnt].to = v;
    edge[cnt].val = w;
    cnt ++;
}
int main() {
    int n;
    while(scanf("%d", &n) != EOF && n) {
        cnt = 0;
        char key01, key02;
        int dist, t;
        for(int i = 0; i < n - 1; ++i) {
            cin >> key01 >> t;
            for(int j = 0; j < t; ++j) {
                cin >> key02 >> dist;
                int u = key01 - 'A';
                int v = key02 - 'A';
                addEdge(u, v, dist);
            }
        }
        sort(edge, edge + cnt, cmp);
        int x = kruskal();
        printf("%d\n", x);
    }
    return 0;
}