K Inverse Pairs Array LeetCode solution in C++

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class Solution {
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 public:
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  int mod = (int)(1e9 + 7);
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  int dp[1001][1001] = {};
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  int kInversePairs(int n, int k) {
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    // base case
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    if (k <= 0) return k == 0;
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    if (dp[n][k] == 0) {
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      dp[n][k] = 1;
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      for (int i = 0; i < n; i++) {
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        dp[n][k] = (dp[n][k] + kInversePairs(n - 1, k - i)) % mod;
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      }
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    }
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    return dp[n][k] - 1;
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  }
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};