蓝桥杯 国王的烦恼

思路：

倒过来用并查集。注意天数不要重复计算。

实现：

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 10005;
const int MAXM = 100005;
int par[MAXN], n, m;
void init(int n) 
{ 
    for (int i = 1; i <= n; i++) par[i] = i; 
}
int find(int x) 
{ 
    if (par[x] == x) return x;
    return par[x] = find(par[x]);
}
void uni(int x, int y)
{
    x = find(x); y = find(y);
    if (x != y) par[x] = y;
}
bool same(int x, int y)
{
    return find(x) == find(y);
}
struct node
{
    int x, y, t;
};
node a[MAXM];
bool cmp(node & a, node & b) { return a.t > b.t; }
int main()
{
    scanf("%d %d", &n, &m);
    init(n);
    for (int i = 0; i < m; i++) scanf("%d %d %d", &a[i].x, &a[i].y, &a[i].t);
    sort(a, a + m, cmp); 
    int cnt = 0, last = -1; 
    for (int i = 0; i < m; i++) 
    {
        if (!same(a[i].x, a[i].y) && a[i].t != last)
        {
            cnt++;
            last = a[i].t;
        }
        uni(a[i].x, a[i].y);
    }
    printf("%d
", cnt);
    return 0;
}