【NOI 2015】 程序自动分析

【题目链接】

https://www.lydsy.com/JudgeOnline/problem.php?id=4195

【算法】

并查集

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN 1000010

struct info
{
        int u,v,w;
} a[MAXN];

int i,n,len,T;
int l[MAXN],r[MAXN],c[MAXN],fa[MAXN<<],t[MAXN<<];
bool flag;

inline int get_root(int x)
{
        if (fa[x] == x) return x;
        return fa[x] = get_root(fa[x]);
}
inline void merge(int u,int v)
{
        int sx = get_root(u),
                sy = get_root(v);
        fa[sx] = sy;
}
inline bool cmp(info a,info b)
{
        return a.w > b.w;
}

int main()
{

        scanf("%d",&T);
        while (T--)
        {
                scanf("%d",&n);
                len = ;
                for (i = ; i <= n; i++)
                {
                        scanf("%d%d%d",&l[i],&r[i],&c[i]);
                        t[++len] = l[i];
                        t[++len] = r[i];
                }
                sort(t+,t+len+);
                len = unique(t+,t+len+) - t - ;
                for (i = ; i <= n; i++)
                {
                        a[i].u = lower_bound(t+,t+len+,l[i]) - t;
                        a[i].v = lower_bound(t+,t+len+,r[i]) - t;
                        a[i].w = c[i];
                }
                sort(a+,a+n+,cmp);
                for (i = ; i <= len; i++) fa[i] = i;
                for (i = ; i; i++)
                {
                        if (a[i].w == )
                                merge(a[i].u,a[i].v);
                        else break;
                }
                flag = false;
                for (; i <= n; i++)
                {
                        if (get_root(a[i].u) == get_root(a[i].v))
                        {
                                flag = true;
                                break;
                        }
                }
                if (flag) printf("NO\n");
                else printf("YES\n");
        }

        return ;

}