The number of duplicates in the array of offer 50

First, the topic

All numbers in an array of length n are within the range of 0 to n-1. Some of the numbers in the array are duplicates, but it is not known that several numbers are duplicates. I don't know how many times each number repeats. Please find any duplicate numbers in the array. For example, if you enter an array of length 7 {2,3,1,0,2,5,3}, the corresponding output is the first repeating number 2.

Second, the idea

Solution One: the solution using Linkedhashmap

Solution Two: See the code (recommended)

Third, the Code

Solution One:

 Packagecn1;ImportJava.util.LinkedHashMap;ImportJava.util.Map;ImportJava.util.Set; Public classSolution { Public BooleanDuplicateintNumbers[],intLengthint[] duplication) {        Booleanflag=false; if(numbers==NULL|| Length==0){            returnFlag; }        //count the number of strings, pay attention to using LinkedhashmapLinkedhashmap<integer, integer> lhm =NewLinkedhashmap<integer, integer>();  for(intnum:numbers) {            if(Lhm.containskey (num)) {lhm.put (num, lhm.get (num)+ 1); } Else{lhm.put (num,1); }        }        //Traverse Map to find the first occurrence of a number        intVal=-1; Set<Map.Entry< Integer, integer>> set =Lhm.entryset ();  for(map.entry< Integer, integer>Es:set) {            intKey =Es.getkey (); intValue =Es.getvalue (); if(Value >= 2) {Val=key;  Break; }        }        if(Val!=-1) {duplication[0]=Val; Flag=true; }        //return Results        returnFlag; }}

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Solution Two:

 Public BooleanDuplicateintNumbers[],intLengthint[] duplication) {        Boolean[] k =New Boolean[length];  for(inti = 0; i < k.length; i++) {            if(K[numbers[i]] = =true) {duplication[0] =Numbers[i]; return true; } K[numbers[i]]=true; }        return false;}

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The number of duplicates in the array of offer 50