Combination Sum IV LeetCode solution in Java

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class Solution {
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  public int combinationSum4(int[] nums, int target) {
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    Integer[] memo = new Integer[target + 1];
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    return recurse(nums, target, memo);
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  }
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  public int recurse(int[] nums, int remain, Integer[] memo) {
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    if (remain < 0) return 0;
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    if (memo[remain] != null) return memo[remain];
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    if (remain == 0) return 1;
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    int ans = 0;
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    for (int i = 0; i < nums.length; i++) {
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      ans += recurse(nums, remain - nums[i], memo);
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    }
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    memo[remain] = ans;
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    return memo[remain];
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  }
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}