Hash Map Patterns

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import java.util.HashMap;
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import java.util.Map;
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public int fn(int[] arr, int k) {
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    Map<Integer, Integer> counts = new HashMap<>();
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    counts.put(0, 1);
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    int ans = 0;
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    int curr = 0;
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    for (int num: arr) {
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        // TODO: logic to change curr
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        ans += counts.getOrDefault(curr - k, 0);
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        counts.put(curr, counts.getOrDefault(curr, 0) + 1);
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    }
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    return ans;
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}

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import java.util.HashSet;
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import java.util.Set;
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public int fn(int[] arr) {
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    Set<Integer> window = new HashSet<>();
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    int ans = 0;
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    int left = 0;
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    for (int right = 0; right < arr.length; right++) {
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        // TODO: add arr[right] to window
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        while (WINDOW_CONDITION_BROKEN) {
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            // TODO: remove arr[left] from window
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            left++;
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        }
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        // TODO: update ans
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    }
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    return ans;
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}