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#include<bits/stdc++.h> | |
using namespace std; | |
#define ll long long int | |
#define FIO ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0) | |
#define mod 1000000007 | |
int main(){ | |
FIO; | |
int t,n,m,k,i,j; | |
string ans; | |
char c; | |
cin >> t; | |
while(t--){ | |
cin >> n >> m; | |
string s[n]; | |
bool valid[n][m],valid2[n][m]; | |
for(i=0;i<n;i++){ | |
cin >> s[i]; | |
for(j=0;j<m;j++){ | |
valid[i][j]=false; | |
valid2[i][j]=false; | |
} | |
} | |
valid[n-1][m-1]=true; | |
for(k=n+m-3;k>=0;k--){ | |
for(i=max(0,k-(m-1));i<n && i<=k;i++){ | |
j=k-i; | |
if(s[i][j]!='#' && i+1<n && valid[i+1][j]) | |
valid[i][j]=true; | |
else if(s[i][j]!='#' && j+1<m && valid[i][j+1]) | |
valid[i][j]=true; | |
} | |
} | |
valid2[0][0]=true; | |
ans=""; | |
ans+=s[0][0]; | |
for(k=1;k<n+m-1;k++){ | |
c='z'; | |
for(i=max(0,k-(m-1));i<n && i<=k;i++){ | |
j=k-i; | |
if(i>0 && valid2[i-1][j] && valid[i][j]) | |
c=min(c,s[i][j]); | |
else if(j>0 && valid2[i][j-1] && valid[i][j]) | |
c=min(c,s[i][j]); | |
} | |
ans+=c; | |
for(i=max(0,k-(m-1));i<n && i<=k;i++){ | |
j=k-i; | |
if(i>0 && valid2[i-1][j] && valid[i][j] && c==s[i][j]) | |
valid2[i][j]=true; | |
else if(j>0 && valid2[i][j-1] && valid[i][j] && c==s[i][j]) | |
valid2[i][j]=true; | |
} | |
} | |
cout << ans << "\n"; | |
} | |
return 0; | |
} |
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