分析

• 删去 $k$ 个之后要是回文串，不过题目会给字符串rearrange，所以对于奇数个数的字符最多留一个，偶数的不用管。

Think Twice, Code Once

#include<bits/stdc++.h>
#define il inline
#define get getchar
#define put putchar
#define is isdigit
#define int long long
#define dfor(i,a,b) for(int i=a;i<=b;++i)
#define dforr(i,a,b) for(int i=a;i>=b;--i)
#define dforn(i,a,b) for(int i=a;i<=b;++i,put(10))
#define mem(a,b) memset(a,b,sizeof a)
#define memc(a,b) memcpy(a,b,sizeof a)
#define pr 114514191981
#define gg(a) cout<<a,put(32)
#define INF 0x7fffffff
#define tt(x) cout<<x<<'\n'
#define ls i<<1
#define rs i<<1|1
#define la(r) tr[r].ch[0]
#define ra(r) tr[r].ch[1]
#define lowbit(x) (x&-x)
using namespace std;
typedef unsigned int ull;
typedef pair<int ,int > pii;
int read(void)
{int x=0,f=1;char c=get();while(!is(c)) (f=c==45?-1:1),c=get();while(is(c)) x=(x<<1)+(x<<3)+(c^48),c=get();return x*f;
}
void write(int x)
{if(x<0) x=-x,put(45);if(x>9) write(x/10);put((x%10)^48);
}
#define writeln(a) write(a),put(10)
#define writesp(a) write(a),put(32)
#define writessp(a) put(32),write(a)
const int N=1e6+10,M=3e4+10,SN=5e3+10,mod=998244353;
int n,k;
char s[N];
signed main()
{int T=read();while(T--){vector<char > ve;unordered_map<char, int > mp;n=read(),k=read();scanf("%s",s+1);if(n-1==k){puts("yes");continue;}dfor(i,1,n) ++mp[s[i]];int cnt=0;for(auto i=mp.begin();i!=mp.end();++i)if(i->second&1) ++cnt;k>=cnt-1?puts("yes"):puts("no");}return 0;
}