leetcode-algorithms/src/CheckIfArrayIsGood.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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// https://leetcode.com/problems/check-if-array-is-good

// T: O(N)

// S: O(N)

import java.util.HashMap;

import java.util.Map;

public class CheckIfArrayIsGood {

public boolean isGood(int[] array) {

final Map<Integer, Integer> frequencies = getFrequencies(array);

for (int i = 1 ; i < array.length - 1 ; i++) {

if (frequencies.getOrDefault(i, 0) != 1) {

return false;

}

return frequencies.getOrDefault(array.length - 1, 0) == 2;

}

private Map<Integer, Integer> getFrequencies(int[] array) {

final Map<Integer, Integer> result = new HashMap<>();

for (int element : array) {

result.put(element, result.getOrDefault(element, 0) + 1);

}

return result;

}

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