Maximum Distance Between Two Occurences Of Same Element - Hashing Problem

To find the maximum distance between two occurrences of same element, we can store the elements in hashmap and compare max index distance. Following is the implementation:

	package hashTables;
	import java.util.HashMap;
	import java.util.Map;
	public class MaxDistanceBtnOccurances {
	public static int maxDistance(int arr[], int n) {
	Map<Integer,Integer> hm = new HashMap<>();
	int max =0,prevMax=0;
	for(int i=0;i<n;i++) {
	if(hm.containsKey(arr[i])) {
	prevMax = i-hm.get(arr[i]);
	if(prevMax>max)
	max=prevMax;
	}else
	hm.put(arr[i],i);
	}
	return max;
	}
	public static void main(String[] args) {
	int a4[]= {3,2,1,2,1,4,5,8,6,7,4,2};
	System.out.println(maxDistance(a4, 12));
	}
	}

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