CF1867D

考虑 -> ，发现符合条件当且仅当形成的基环树环长为，注意要特判

#include <bits/stdc++.h>
/*
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
*/
using namespace std;

const double eps = 1e-10;
const double pi = 3.1415926535897932384626433832795;
const double eln = 2.718281828459045235360287471352;

#define f(i, a, b) for (int i = a; i <= b; i++)
#define scan(x) scanf("%d", &x)
#define mp make_pair
#define pb push_back
#define lowbit(x) (x&(-x))

#define fi first
#define se second
#define SZ(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define summ(a) (accumulate(all(a), 0ll))

typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;

using ll=long long;

struct dsu{
    vector<int> fa,sz;
    dsu(int n){
        fa.resize(n+1),sz.resize(n+1);
        for(int i=1;i<=n;++i)fa[i]=i,sz[i]=1;
    }
    int fnd(int x){
        return fa[x]==x?x:fa[x]=fnd(fa[x]);
    }
    bool merge(int x ,int y){
        int oa=fnd(x),ob=fnd(y);
        if(oa!=ob){
            fa[ob]=oa,sz[oa]+=sz[ob];
            return true;
        }
        return false;
    }
};

int tt,n,k,b[(int)1e5+9];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>tt;
    while(tt--){
        cin>>n>>k;
        dsu d(n);
        vector<vector<int>> g(n+1,vector<int>());
        vector<int> dis(n+1,0);
        bool same=true;
        for(int i=1;i<=n;++i){
            cin>>b[i];
            d.merge(i,b[i]),g[i].push_back(b[i]);
            same&=b[i]==i;
        }

        auto dfs=[&](auto self,int u,int fa,int dep)->ll{
            dis[u]=dep;
            ll res=0ll;
            for(auto it:g[u]){
                if(dis[it])res=max(res,dep-dis[it]+1ll);
                else res=max(res,self(self,it,u,dep+1));
            }
            //cerr<<res<<"::\n";
            return res;
        };

        bool ok=true;
        if(k==1&&!same)ok=false;
        f(i,1,n)if(d.fnd(i)==i)ok&=dfs(dfs,i,0,1)==k;
        cout<<(ok?"YES\n":"NO\n");

    }
    return 0;
}