algorithm - Way to judge if two Arrays are identical? -


by identical mean 2 arrays contain same elements, order of elements in arrays not matter here.

the solution came this(which turns out wrong approach pointed out in comments): 

  if size of 2 arrays equal  see true, find elements of array in array b  found,  find elements of array b in array  found, conclusion 2 arrays identical

however, there better algorithm in term of time complexity?

let's have user[] array 1 , user[] array 2. can lop through array 1 , add them dictionary<user, int> dictionary key user , value count. loop through second array , each user in array 2 decrement count in dictionary (if count greater 1) or remove element (if count 1). if user isn't in dictionary, can stop, arrays don't match.

if end , had checked length of arrays same, arrays match. if hadn't checked length earlier (which of course still should have), can verify dictionary empty after looping through array 2.

i don't know performance of is, faster sorting both lists , looping through them comparing element element. takes more memory though, if arrays not super large memory usage shouldn't issue.


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