HDU-4313 matrix least Spanning Tree, set Division

The question is how to minimize the cost of opening a tree without any other similar nodes.

We sort the edge in order from large to small, and then check whether this edge can connect two similar nodes. If yes, this edge is the edge to be selected. First, the feature value is retained and expanded to the mark point through the query set.

The Code is as follows:

#include <cstring>#include <cstdlib>#include <cstdio>#include <map>#include <algorithm>using namespace std;int N, M, set[100005], have[100005];struct Edge{    int x, y, fee;    bool operator < (Edge t) const    {        return fee > t.fee;    }}e[100005];int find(int x){    return set[x] = x == set[x] ? x : find(set[x]);}void merge(int a, int b){    set[a] = b;    if (have[a]) {        have[b] = 1;    }}int main(){    int T, a, b, c;    long long int sum;    scanf("%d", &T);    while (T--) {        sum = 0;        memset(have, 0, sizeof (have));        map<int,int>mp;        scanf("%d %d", &N, &M);        set[N-1] = N-1;        for (int i = 0; i < N-1; ++i) {            scanf("%d %d %d", &e[i].x, &e[i].y, &e[i].fee);            set[i] = i;        }        for (int i = 0; i < M; ++i) {            scanf("%d", &c);             have[c] = 1;        }        sort(e, e + N - 1);        for (int i = 0; i < N-1; ++i) {            int a = find(e[i].x), b = find(e[i].y);            if (have[a] && have[b]) {                sum += e[i].fee;                continue;            }            merge(a, b);        }        printf("%I64d\n", sum);    }    return 0;}