front11 challenge

Hi,

I am trying below challenge

http://codingbat.com/prob/p128270

public int[] front11(int[] a, int[] b) {
  int len1=a.length;
  int len2=b.length;
  
  int[] c=new int[2];
  
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[1];
  return c;
  }
  
    if(len1>=1&len2==0){  
  c[0]=a[0];
  c[1]=0;
  return c;
  }
  
  
  
    if(len1==0&len2>=1){  
  c[0]=0;
  c[1]=b[1];
  return c;
  }
  
  else{
  return null;
  }
  
}

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i failed tests.

when to say
c[0]=0;
when to say
c[0]==0;

how to fix and improve my code and alternate ways of doing it. please advise
LVL 7
gudii9Asked:
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ozoCommented:
say c[0]=0; when you are setting c[0] to 0
say c[0]==0 when you are testing whether c[0] is 0
ozoCommented:
public int[] front11(int[] a, int[] b) {
  int lena=a.length;
  int lenb=b.length;
 
  int[] c=new int[(lena>0?1:0)+(lenb>0?1:0)];
 
  if(lena>=1&lenb>=1){  
  c[0]=a[0];
  c[1]=b[0];
  }
 
  if(lena>=1&lenb==0){  
  c[0]=a[0];
  }
 
  if(lena==0&lenb>=1){  
  c[0]=b[0];
  }
 
  return c;
 }

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krakatoaCommented:
public int[] front11(int[] a, int[] b) {
  return a.length==0&&b.length==0?new int[]{}:a.length==0?new int[] {b[0]}:b.length==0?new int[]{a[0]}:new int[]{a[0],b[0]};
}

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krakatoaCommented:
Here's another, short "if" arrangement :

public int[] front11(int[] a, int[] b) {
  if (a.length+b.length==0){return new int[]{};}
  if(a.length==0){return new int[]{b[0]};}
  if(b.length==0){return new int[] {a[0]};}
  return new int[]{a[0],b[0]};
}

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krakatoaCommented:
. . .  and in this bit of your code :

else{
  return null;
  }

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you are returning 'null'. But the challenge asks you to return an int array  - so why are you returning 'null'? You must return the required type. If the product of one of your code passages holds no values, then return an empty container of that type - in this case an empty int[].
gudii9Author Commented:
public int[] front11(int[] a, int[] b) {
  int len1=a.length;
  int len2=b.length;
  
  int[] c=new int[(len1>0?1:0)+(len2>0?1:0)];
  
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[0];
  return c;
  }
  
    if(len1>=1&len2==0){  
  c[0]=a[0];
  //c[1]=0;
  return c;
  }
  
  
  
    if(len1==0&len2>=1){  
 // c[0]=0;
  c[1]=b[1];
  return c;
  }
  
  else{
  return null;
  }
  
}

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i modified as above and failing few tests. please advise where i am making mistake
gudii9Author Commented:
public int[] front11(int[] a, int[] b) {
  int len1=a.length;
  int len2=b.length;
  
  int[] c=new int[(len1>0?1:0)+(len2>0?1:0)];
  
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[0];
  return c;
  }
  
    if(len1>=1&len2==0){  
  c[0]=a[0];
  //c[1]=0;
  return c;
  }
  
  
  
    if(len1==0&len2>=1){  
 // c[0]=0;
  c[1]=b[0];
  return c;
  }
  
  else{
  return null;
  }
  
}

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i corrected below highlighted
 // c[0]=0;
  c[1]=b[0];
  return c;

still getting error. please advise





Show output only (no red/green)
prev  |  next  |  chance   |  CodingBat  >  Array-1      
Expected      Run            
front11({1, 2, 3}, {7, 9, 8}) → {1, 7}      {1, 7}      OK         
front11({1}, {2}) → {1, 2}      {1, 2}      OK         
front11({1, 7}, {}) → {1}      {1}      OK         
front11({}, {2, 8}) → {2}      {xception:java.lang.ArrayIndexOutOfBoundsException: 1 (line number:23}      X         
front11({}, {}) → {}      {ul}      X
gudii9Author Commented:
i corrected further as highlighted

public int[] front11(int[] a, int[] b) {
  int len1=a.length;
  int len2=b.length;
 
  int[] c=new int[(len1>0?1:0)+(len2>0?1:0)];
 
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[0];
  return c;
  }
 
    if(len1>=1&len2==0){  
  c[0]=a[0];
  //c[1]=0;
  return c;
  }
 
 
 
    if(len1==0&len2>=1){  
 // c[0]=0;
  c[0]=b[0];
  return c;
  }
 
  else{
  return null;
  }
 
}

still failing one test case

front11({}, {}) → {}      {ul}      X         
please advise
ozoCommented:
public int[] front11(int[] a, int[] b) {
  int len1=a.length;
  int len2=b.length;
  
  int[] c=new int[(len1>0?1:0)+(len2>0?1:0)];
  
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[0];
  return c;
  }
  
    if(len1>=1&len2==0){  
  c[0]=a[0];
  //c[1]=0;
  return c;
  }
  
  
  
    if(len1==0&len2>=1){  
 // c[0]=0;
  c[0]=b[0]; //  c[1]=b[1];
  return c;
  }
  
  else{
  return c; //return null;
  }
  
}

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krakatoaCommented:
public int[] front11(int[] a, int[] b) {
   int len1=a.length;
  int len2=b.length;
  
  int[] c=new int[(len1>0?1:0)+(len2>0?1:0)];
  
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[0];
  return c;
  }
  
    if(len1>=1&len2==0){  
  c[0]=a[0];
  //c[1]=0;
  return c;
  }
  
  
  
    if(len1==0&len2>=1){  
 // c[0]=0;
  c[0]=b[0];
  return c;
  }
  
  else{
  return new int[]{};
  }
  
}

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gudii9Author Commented:
public int[] front11(int[] a, int[] b) {
  int len1=a.length;
  int len2=b.length;
  
  int[] c=new int[(len1>0?1:0)+(len2>0?1:0)];
  
  if(len1>=1&len2>=1){  
  c[0]=a[0];
  c[1]=b[0];
  return c;
  }
  
    if(len1>=1&len2==0){  
  c[0]=a[0];
  //c[1]=0;
  return c;
  }
  
  
  
    if(len1==0&len2>=1){  
 // c[0]=0;
  c[0]=b[0]; //  c[1]=b[1];
  return c;
  }
  
  else{
  return c; //return null;
  }
  
}

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above solution worked but it has shaken my wrong concept that 'method needs to have separate return statement apart from if block return statement and else block return statement'
krakatoaCommented:
ozoCommented:
The correct concept is that all paths need a return
(unless the method is declared void)
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