Bilgisayar Dünyam: Dizide Ardışığı Bulunan Sayıları Sayma

6 Nisan 2020 Pazartesi

O(n) time, O(n) space complexity

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	import java.util.*;
	import java.util.stream.*;

	class CountingConsecutiveElements {

	public int countElements(int[] arr) {

	Map<Integer, Integer> numberCounts = new HashMap<>();
	for(int num : arr) {
	Integer wrappedNum = Integer.valueOf(num);
	int currentCount = numberCounts.getOrDefault(wrappedNum,0);
	numberCounts.put(wrappedNum,currentCount+1);
	}

	int result = 0;

	for(Map.Entry<Integer, Integer> currentEntry: numberCounts.entrySet()) {
	int currentNum = currentEntry.getKey().intValue();
	int currentCount = currentEntry.getValue().intValue();

	int relatedNumCount = numberCounts.getOrDefault(currentNum+1, 0);

	// Even if there is only one x+1, count all x's. E.g. [1,2,2]
	result += relatedNumCount == 0 ? 0 : currentCount;
	}

	return result;
	}
	}