Arithmetic Slices II - Subsequence LeetCode solution in Java

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class Solution {
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  public int numberOfArithmeticSlices(int[] nums) {
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    int n = nums.length;
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    HashMap<Integer, Integer>[] dp = new HashMap[n];
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    for (int i = 0; i < n; i++) {
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      dp[i] = new HashMap<Integer, Integer>();
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    }
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    int ans = 0;
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    for (int i = 1; i < n; i++) {
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      for (int j = 0; j < i; j++) {
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        long cd = (long) nums[i] - (long) nums[j];
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        if (cd <= Integer.MIN_VALUE || cd >= Integer.MAX_VALUE) {
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          continue;
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        }
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        int endingAtj = dp[j].getOrDefault((int) cd, 0);
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        int endingAti = dp[i].getOrDefault((int) cd, 0);
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        ans += endingAtj;
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        dp[i].put((int) cd, endingAtj + endingAti + 1);
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      }
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    }
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    return ans;
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  }
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}