pta九宫格输入法怎么理解这个代码

Question

```

#include <stdio.h>

int main()

{
int i,j,len1,len2,t,k=0;
char a[10][6]={"0 ","1,.?!","2ABC","3DEF","4GHI","5JKL","6MNO","7PQRS","8TUV","9WXYZ","0 "};
char b[1000];
gets(b);
len2=strlen(b);
for(i=0;i<len2;i++)
{
t=b[i]-'0';
len1=strlen(a[t]);
while(b[i]!=' '&&b[i]!='\0')
{
i++;
k++;
}
j=k%len1==0?len1-1:k%len1-1;
printf("%c",a[t][j]);
k=0;
}
printf("\n");
return 0;
}```