Minimum Space Wasted From Packaging LeetCode solution in Java

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class Solution {
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  public int minWastedSpace(int[] packages, int[][] boxes) {
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    Arrays.sort(packages);
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    int n = packages.length, k = -1;
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    long sum = 0, ans = Long.MAX_VALUE;
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    int[] pos = new int[100001];
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    for (int i = 0; i < 100001; i++) { // precompute jump position.
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      while (k < n - 1 && packages[k + 1] == i) {
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        sum += packages[++k];
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      }
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      pos[i] = k;
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    }
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    for (int[] b : boxes) {
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      Arrays.sort(b);
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      long cost = -sum;
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      k = -1;
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      for (int i = 0; i < b.length; i++) {
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        if (pos[b[i]] >= 0) {
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          int cnt = pos[b[i]] - k;
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          cost += 1L * cnt * b[i];
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          k = pos[b[i]];
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        }
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      }
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      ans = k == n - 1 ? Math.min(cost, ans) : ans;
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    }
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    return ans == Long.MAX_VALUE ? -1 : (int) (ans % (int) (1e9 + 7));
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  }
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}