Can someone explain this to me?

I'm no good with for loops.

My friend wrote this and i didn't fully understand it when he explained, so if anyone can explain simply how it works, i know what it is supposed to do but does not work, so i want to understand it before i fix it.

Code (CSharp):

1. public bool CheckifDone()
2.     {
3.  
4.         bool done = true;
5.         for (int i = 0; i < Alive.Count; i++)
6.         {
7.             bool inDead = false;
8.             for (int x = 0; x < Dead.Count; x ++)
9.             {
10.                 if (Alive[i] == Dead[x])
11.                 {
12.                     Dead.Add (Alive [i]);
13.                 }
14.             }
15.             if (inDead == false)
16.             {
17.                 done = false;
18.                 toKill.Add(Alive[i]);
19.             }
20.  
21.         }
22.         for (int y = 0; y < toKill.Count; y++)
23.         {
24.             Alive.Remove(toKill[y]);
25.         }
26.  
27.         return done;
28.  
29.     }

 

Ok, so what is it supposed to do?

 

That.

Code (CSharp):

1.             for (int x = 0; x < Dead.Count; x ++)
2.             {
3.                 if (Alive[i] == Dead[x])
4.                 {
5.                     Dead.Add (Alive [i]);
6.                 }
7.             }

And, the array is modified while you iterate over it... wait. If you enter that if-block, you'll be stuck in an infinite loop, because the last element added to the Dead will be always Alive\[i\] .

 

Without knowing anything about the purpose of this code, and without knowing what these array types are, here are my comments as I read through it:

Code (CSharp):

1. public bool CheckifDone() {                   // we're checking if something is done
2.  
3.     bool done = true;                         // initialize done to true
4.     for(int i = 0; i < Alive.Count; i++) {    // for each alive thing
5.         bool inDead = false;                  // initialize inDead to false
6.         for(int x = 0; x < Dead.Count; x++) { // for each dead thing
7.             if(Alive[i] == Dead[x]) {         // if the dead thing is the same object as the alive thing
8.                 Dead.Add(Alive[i]);           // add the alive thing to the dead list (isn't it already in the list??)
9.             }
10.         }
11.         if(inDead == false) {                 // this is guaranteed false, because nothing changed it from earlier
12.             done = false;                     // guaranteed to be set, due to above
13.             toKill.Add(Alive[i]);             // kill the alive thing (this will be done for all alive things, due to above)
14.         }
15.  
16.     }
17.     for(int y = 0; y < toKill.Count; y++) {   // loop through all things to kill (all alive things, due to above)
18.         Alive.Remove(toKill[y]);              // remove them from the alive list (Alive list now empty)
19.     }
20.  
21.     return done;                              // this will always return false, due to above
22.  
23. }