c - switch without break and i++ vs ++i -

I do not understand why both of them have different output

there are two simple There are C programs

  int main () {int i; For (i = 0; i   
 gives output: after zero two to two two  
 after switch in this case when I can change value from 0 to 1 in the variable ?  
  int main () {int i; For (i = 0; i   
 This interchange: a two end   
 
 < The former>  switch (i ++) {}   
 is the same:  
  int j = i; I ++; Switch (j) {}   
 While  
  switch (++ i) {}   
 is the same As:  
  i ++; Switch (i) {}