Educational Codeforces Round 143 (Rated for Div. 2)
A. Two Towers
拼接序列。枚举相邻相同字母。如果 \(>1\) 则无解。否则可以做一个断点，有解。
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// Problem: A. Two Towers
// Contest: Codeforces - Educational Codeforces Round 143 (Rated for Div. 2)
// URL: https://codeforces.com/contest/1795/problem/A
// Memory Limit: 256 MB
// Time Limit: 2000 ms
//
// Powered by CP Editor (https://cpeditor.org)
#include <bits/stdc++.h>
using namespace std;
#define Multicase() for(int T = read() ; T ; T--)
#define lowbit(x) (x & (-x))
#define ls(p) (p<<1)
#define rs(p) (p<<1|1)
#define l(p) tree[p].ls
#define r(p) tree[p].rs
#define sum(p) tree[p].sum
#define tag(p) tree[p].tag
#define F(i,a,b) for(int i=(a) ;i<=(b);++i)
#define F2(i,a,b) for(int i=(a);i< (b);++i)
#define dF(i,a,b) for(int i=(a);i>=(b);--i)
#define debug(...) fprintf(stderr,__VA_ARGS__)
#define Debug debug("Passing [%s] in LINE %d\n",__FUNCTION__,__LINE__)
#define clr(a,x) memset(a,x,sizeof(a))
#define pb push_back
#define mkp make_pair
#define fi first
#define se second
#define endl '\n'
#define ENDL putchar('\n')
#define forGraph(u) for(int i=head[u];i;i=G[i].next)
const int N=5e5+5;
const int M=1e6+5;
const int MN=1e3+5;
const int iinf=INT_MAX;
const double eps=1e-9;
const double pi=acos(-1);
const long long linf=LLONG_MAX;
const long long mod=1000000007,mod2=998244353;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef map<int,int> mii;
typedef map<ll,ll> mll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef map<string,int> msi;
inline int read(){int x(0), f(0); char ch=getchar(); while(ch<'0'||ch>'9'){f|=ch=='-';ch=getchar();} while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48); ch=getchar();} return f?-x:x;}
template <typename T> void read(T &x){x=0; T f(0); char ch=getchar(); while(ch<'0'||ch>'9'){f|=ch=='-';ch=getchar();} while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48); ch=getchar();} x=f?-x:x;}
template <typename T,typename ...Arg>void read(T& x,Arg& ...arg){read(x);read(arg...);}
template <typename T> inline void write(T x){static char buf[64]; static int tot(0); if(x<0) putchar('-'),x=-x; do buf[++tot]=(x%10)+48,x/=10; while(x); do putchar(buf[tot--]); while(tot);}
template <typename T> void write(T x,char c){static char buf[64]; static int tot(0); if(x<0) putchar('-'),x=-x; do buf[++tot]=(x%10)+48,x/=10; while(x); do putchar(buf[tot--]); while(tot); putchar(c);}
void judge(bool x){printf(x?"YES\n":"NO\n");}
void Solve();
struct Graph{
int to,w,next;
}G[M<<1];
int head[N],cnt;
void addEdge(int u,int v,int w=1){G[++cnt]=(Graph){v,w,head[u]}; head[u]=cnt;}
template<class T,class U> void chkmax(T &x, U y) { if(x < y) x = y; }
template<class T,class U> void chkmin(T &x, U y) { if(x > y) x = y; }
int n,m,q,k,p;
int a[N],b[N],f[N];
vector<int> v;
int main(){
Multicase()
Solve();
}
string s,t;
void Solve(){
p=0;
read(n,m);
cin>>s>>t;
reverse(t.begin(),t.end());
s+=t;
F(i,1,n+m-1) if(s[i]==s[i-1]) p++;
if(p<=1) judge(1);
else judge(0);
}