How to search a string in String array

Question

I need to search a string in the string array  I dont want to use any for looping in it  string    arr     One   Two   Three     string theString    One    I need to check whether theString variable is present in arr

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Each class implementing IList has a method Contains Object value   And so does System Array

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Each class implementing IList has a method Contains Object value   And so does System Array

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I think it is better to use Array Exists than Array FindAll

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Well  something is going to have to look  and looping is more efficient than recursion  since tail-end recursion isn t fully implemented     so if you just don t want to loop yourself  then either of   bool has   arr Contains var       NET 3 5   or  bool has   Array IndexOf arr  var   gt   0    For info  avoid names like var - this is a keyword in C  3 0

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Why the prohibition  I don t want to use any looping   That s the most obvious solution  When given the chance to be obvious  take it    Note that calls like arr Contains      are still going to loop  it just won t be you who has written the loop   Have you considered an alternate representation that s more amenable to searching    A good Set implementation would perform well   HashSet  TreeSet or the local equivalent   If you can be sure that arr is sorted  you could use binary search  which would need to recurse or loop  but not as often as a straight linear search

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At first shot  I could come up with something like this  but it s pseudo code and assuming you cannot use any  NET built-in libaries   Might require a bit of tweaking and re-thinking  but should be good enough for a head-start  maybe   int findString String var  String   stringArray  int currentIndex  int stringMaxIndex            if currentIndex  gt  stringMaxIndex         return  -stringMaxIndex-1       else if var  arr currentIndex    or use any string comparison op or function        return 0      else         return findString var  stringArray  currentIndex    stringMaxIndex    1                  calling code     int index   findString var  arr  0  getMaxIndex arr         if index    -1 printOnScreen  Not found        else printOnScreen  Found on index      index

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Well  something is going to have to look  and looping is more efficient than recursion  since tail-end recursion isn t fully implemented     so if you just don t want to loop yourself  then either of   bool has   arr Contains var       NET 3 5   or  bool has   Array IndexOf arr  var   gt   0    For info  avoid names like var - this is a keyword in C  3 0

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Its pretty simple  I always use this code to search string from a string array  string   stringArray      text1    text2    text3    text4     string value    text3   int pos   Array IndexOf stringArray  value   if  pos  gt  -1        return true    else       return false

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Why the prohibition  I don t want to use any looping   That s the most obvious solution  When given the chance to be obvious  take it    Note that calls like arr Contains      are still going to loop  it just won t be you who has written the loop   Have you considered an alternate representation that s more amenable to searching    A good Set implementation would perform well   HashSet  TreeSet or the local equivalent   If you can be sure that arr is sorted  you could use binary search  which would need to recurse or loop  but not as often as a straight linear search

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I m surprised that no one suggested using Array IndexOf Method  Indeed  Array IndexOf has two advantages    It allows searching if an element is included into an array  It gets at the same time the index into the array   int stringIndex   Array IndexOf arr  theString   if  stringIndex  gt   0           theString has been found    Inline version   if  Array IndexOf arr  theString   gt   0           theString has been found

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Each class implementing IList has a method Contains Object value   And so does System Array

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it is old one  but this is the way i do it   enter code herevar result   Array Find names  element   gt  element     quot One quot

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If the array is sorted  you can use BinarySearch  This is a O log n  operation  so it is faster as looping  If you need to apply multiple searches and speed is a concern  you could sort it  or a copy  before using it

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bool exists   arr Contains  One

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Does it have to be a string      A List lt String gt  would give you what you need   List lt String gt  testing   new List lt String gt     testing Add  One    testing Add  Two    testing Add  Three    testing Add  Mouse    bool inList   testing Contains  Mouse

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At first shot  I could come up with something like this  but it s pseudo code and assuming you cannot use any  NET built-in libaries   Might require a bit of tweaking and re-thinking  but should be good enough for a head-start  maybe   int findString String var  String   stringArray  int currentIndex  int stringMaxIndex            if currentIndex  gt  stringMaxIndex         return  -stringMaxIndex-1       else if var  arr currentIndex    or use any string comparison op or function        return 0      else         return findString var  stringArray  currentIndex    stringMaxIndex    1                  calling code     int index   findString var  arr  0  getMaxIndex arr         if index    -1 printOnScreen  Not found        else printOnScreen  Found on index      index

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bool exists   arr Contains  One

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Every method  mentioned earlier does looping either internally or externally  so it is not really important how to implement it  Here another example of finding all references of target string         string    arr     One   Two   Three           var target    One          var results   Array FindAll arr  s   gt  s Equals target

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In C   if you can use an ArrayList  you can use the Contains method  which returns a boolean   if MyArrayList Contains  One

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bool exists   arr Contains  One

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You can use Find method of Array type  From  NET 3 5 and higher    public static T Find lt T gt       T   array      Predicate lt T gt  match     Here is some examples      we search an array of strings for a name containing the letter    a     static void Main       string   names      Rodney    Jack    Jill       string match   Array Find  names  ContainsA     Console WriteLine  match          Jack   static bool ContainsA  string name    return name Contains   a        Here   s the same code shortened with an anonymous method   string   names      Rodney    Jack    Jill     string match   Array Find  names  delegate  string name      return name Contains   a            Jack   A lambda expression shortens it further   string   names      Rodney    Jack    Jill     string match   Array Find  names  n   gt  n Contains   a            Jack

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Why the prohibition  I don t want to use any looping   That s the most obvious solution  When given the chance to be obvious  take it    Note that calls like arr Contains      are still going to loop  it just won t be you who has written the loop   Have you considered an alternate representation that s more amenable to searching    A good Set implementation would perform well   HashSet  TreeSet or the local equivalent   If you can be sure that arr is sorted  you could use binary search  which would need to recurse or loop  but not as often as a straight linear search

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In C   if you can use an ArrayList  you can use the Contains method  which returns a boolean   if MyArrayList Contains  One

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Does it have to be a string      A List lt String gt  would give you what you need   List lt String gt  testing   new List lt String gt     testing Add  One    testing Add  Two    testing Add  Three    testing Add  Mouse    bool inList   testing Contains  Mouse

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Each class implementing IList has a method Contains Object value   And so does System Array

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Its pretty simple  I always use this code to search string from a string array  string   stringArray      text1    text2    text3    text4     string value    text3   int pos   Array IndexOf stringArray  value   if  pos  gt  -1        return true    else       return false

User · Answer

If the array is sorted  you can use BinarySearch  This is a O log n  operation  so it is faster as looping  If you need to apply multiple searches and speed is a concern  you could sort it  or a copy  before using it

User · Answer

Does it have to be a string      A List lt String gt  would give you what you need   List lt String gt  testing   new List lt String gt     testing Add  One    testing Add  Two    testing Add  Three    testing Add  Mouse    bool inList   testing Contains  Mouse

User · Answer

In C   if you can use an ArrayList  you can use the Contains method  which returns a boolean   if MyArrayList Contains  One

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I m surprised that no one suggested using Array IndexOf Method  Indeed  Array IndexOf has two advantages    It allows searching if an element is included into an array  It gets at the same time the index into the array   int stringIndex   Array IndexOf arr  theString   if  stringIndex  gt   0           theString has been found    Inline version   if  Array IndexOf arr  theString   gt   0           theString has been found

User · Answer

At first shot  I could come up with something like this  but it s pseudo code and assuming you cannot use any  NET built-in libaries   Might require a bit of tweaking and re-thinking  but should be good enough for a head-start  maybe   int findString String var  String   stringArray  int currentIndex  int stringMaxIndex            if currentIndex  gt  stringMaxIndex         return  -stringMaxIndex-1       else if var  arr currentIndex    or use any string comparison op or function        return 0      else         return findString var  stringArray  currentIndex    stringMaxIndex    1                  calling code     int index   findString var  arr  0  getMaxIndex arr         if index    -1 printOnScreen  Not found        else printOnScreen  Found on index      index

User · Answer

You can check the element existence by   arr Any x   gt  x     One

User · Answer

I think it is better to use Array Exists than Array FindAll

User · Answer

You can use Find method of Array type  From  NET 3 5 and higher    public static T Find lt T gt       T   array      Predicate lt T gt  match     Here is some examples      we search an array of strings for a name containing the letter    a     static void Main       string   names      Rodney    Jack    Jill       string match   Array Find  names  ContainsA     Console WriteLine  match          Jack   static bool ContainsA  string name    return name Contains   a        Here   s the same code shortened with an anonymous method   string   names      Rodney    Jack    Jill     string match   Array Find  names  delegate  string name      return name Contains   a            Jack   A lambda expression shortens it further   string   names      Rodney    Jack    Jill     string match   Array Find  names  n   gt  n Contains   a            Jack

User · Answer

If the array is sorted  you can use BinarySearch  This is a O log n  operation  so it is faster as looping  If you need to apply multiple searches and speed is a concern  you could sort it  or a copy  before using it

User · Answer

Every method  mentioned earlier does looping either internally or externally  so it is not really important how to implement it  Here another example of finding all references of target string         string    arr     One   Two   Three           var target    One          var results   Array FindAll arr  s   gt  s Equals target

User · Answer

At first shot  I could come up with something like this  but it s pseudo code and assuming you cannot use any  NET built-in libaries   Might require a bit of tweaking and re-thinking  but should be good enough for a head-start  maybe   int findString String var  String   stringArray  int currentIndex  int stringMaxIndex            if currentIndex  gt  stringMaxIndex         return  -stringMaxIndex-1       else if var  arr currentIndex    or use any string comparison op or function        return 0      else         return findString var  stringArray  currentIndex    stringMaxIndex    1                  calling code     int index   findString var  arr  0  getMaxIndex arr         if index    -1 printOnScreen  Not found        else printOnScreen  Found on index      index

User · Answer

Why the prohibition  I don t want to use any looping   That s the most obvious solution  When given the chance to be obvious  take it    Note that calls like arr Contains      are still going to loop  it just won t be you who has written the loop   Have you considered an alternate representation that s more amenable to searching    A good Set implementation would perform well   HashSet  TreeSet or the local equivalent   If you can be sure that arr is sorted  you could use binary search  which would need to recurse or loop  but not as often as a straight linear search

User · Answer

Well  something is going to have to look  and looping is more efficient than recursion  since tail-end recursion isn t fully implemented     so if you just don t want to loop yourself  then either of   bool has   arr Contains var       NET 3 5   or  bool has   Array IndexOf arr  var   gt   0    For info  avoid names like var - this is a keyword in C  3 0

User · Answer

it is old one  but this is the way i do it   enter code herevar result   Array Find names  element   gt  element     quot One quot

User · Answer

Every method  mentioned earlier does looping either internally or externally  so it is not really important how to implement it  Here another example of finding all references of target string         string    arr     One   Two   Three           var target    One          var results   Array FindAll arr  s   gt  s Equals target

User · Answer

Every method  mentioned earlier does looping either internally or externally  so it is not really important how to implement it  Here another example of finding all references of target string         string    arr     One   Two   Three           var target    One          var results   Array FindAll arr  s   gt  s Equals target

User · Answer

In C   if you can use an ArrayList  you can use the Contains method  which returns a boolean   if MyArrayList Contains  One

User · Answer

Does it have to be a string      A List lt String gt  would give you what you need   List lt String gt  testing   new List lt String gt     testing Add  One    testing Add  Two    testing Add  Three    testing Add  Mouse    bool inList   testing Contains  Mouse

User · Answer

If the array is sorted  you can use BinarySearch  This is a O log n  operation  so it is faster as looping  If you need to apply multiple searches and speed is a concern  you could sort it  or a copy  before using it

User · Answer

bool exists   arr Contains  One

User · Answer

You can check the element existence by   arr Any x   gt  x     One

User · Answer

Well  something is going to have to look  and looping is more efficient than recursion  since tail-end recursion isn t fully implemented     so if you just don t want to loop yourself  then either of   bool has   arr Contains var       NET 3 5   or  bool has   Array IndexOf arr  var   gt   0    For info  avoid names like var - this is a keyword in C  3 0

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