离散化

离散化

先将数组升序排序，然后去重。

for(int i = 1; i <= n; i++)
{
     scanf("%d%d%d", &a[i], &b[i], &c[i]);
     d[++cnt] = a[i];
     d[++cnt] = b[i];
 }
 sort(d+1, d+1+cnt);
 cnt = unique(d + 1, d + cnt + 1) - (d+1);
 init(cnt);
 for(int i = 1; i <= n; i++)
 {
     a[i] = lower_bound(d+1, d+1+cnt, a[i]) - d;
     b[i] = lower_bound(d+1, d+1+cnt, b[i]) - d;
 }

例如$a[1]=1，a[2]=3，a[3]=1e4，a[4]=1e7，a[5]=9，b[1]=1e4，b[2]=1e5，b[3]=10，b[4]=8，b[5]=1e7。$
离散化后$a[1]=1，a[2]=2，a[3]=6，a[4]=8，a[5]=4，b[1]=6，b[2]=7，b[3]=5，b[4]=3，b[5]=8。$
例题
添加链接描述
code

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 5e6+5;
const ll mod = 1e9+7;
int n, fa[N], cnt, t, a[N], b[N], c[N], d[N];
void init(int n)
{
    for(int i = 1; i <= n; i++)
        fa[i] = i;
}
int find(int x)
{
    return (x == fa[x] ? x : fa[x] = find(fa[x]));
}
void merge(int x, int y)
{
    fa[find(x)] = find(y);
}
int main()
{
    scanf("%d", &t);
    while(t--)
    {
        cnt = 0;
        scanf("%d", &n);
        ///离散化
        for(int i = 1; i <= n; i++)
        {
            scanf("%d%d%d", &a[i], &b[i], &c[i]);
            d[++cnt] = a[i];
            d[++cnt] = b[i];
        }
        sort(d+1, d+1+cnt);
        cnt = unique(d + 1, d + cnt + 1) - (d+1);
        init(cnt);
        for(int i = 1; i <= n; i++)
        {
            a[i] = lower_bound(d+1, d+1+cnt, a[i]) - d;
            b[i] = lower_bound(d+1, d+1+cnt, b[i]) - d;
        }
        int flag = 1;
        for(int i = 1; i <= n; i++)
            if(c[i] == 1)
                merge(a[i], b[i]);
        for(int i = 1; i <= n; i++)
            if(c[i] != 1)
            {
                int fx = find(a[i]), fy = find(b[i]);
                if(fx == fy)
                {
                    flag = 0;
                    break;
                }
            }
        if(flag)
            cout << "YES" << endl;
        else
            cout << "NO" << endl;
    }
    return 0;
}