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jackoup
c_cpp
10 months ago
618 B
4
Indexable
CodeForces
#include <iostream> #include <vector> using namespace std; void fio() { ios::sync_with_stdio(false),cin.tie(0),cout.tie(0); } int main() { fio(); int n;cin>>n; int m;cin>>m; char ans= ' '; for(int i =0;i<n;i++) { string myInput;cin>>myInput; if( i != 0 && myInput[0] == ans){ cout<<"NO"; return 0; } for(int j =1 ;j<m;j++) { if(myInput[j] != myInput[0]){ cout<<"NO"; return 0; } } ans = myInput[0]; } cout<<"YES"; return 0; }
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