Given an integer array arr, count element x such that x + 1 is also in arr. If there're duplicates in arr, count them seperately. https://leetcode.com/explore/challenge/card/30-day-leetcoding-challenge/528/week-1/3289/

CountingConsecutiveElements.java

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;
    }
}