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Solution.cs
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37 lines (35 loc) · 998 Bytes
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public class Solution
{
public int SumOfFlooredPairs(int[] nums)
{
int mod = 1000000007;
int maxVal = 0;
foreach (int num in nums)
{
maxVal = Math.Max(maxVal, num);
}
long ans = 0;
int[] freq = new int[maxVal + 1];
foreach (int num in nums)
{
freq[num]++;
}
int[] prefixSums = new int[maxVal + 1];
for (int i = 1; i < maxVal + 1; i++)
{
prefixSums[i] = prefixSums[i - 1] + freq[i];
}
for (int i = 1; i <= maxVal; i++)
{
if (freq[i] == 0) continue;
for (int k = 1; (k * i) <= maxVal; k++)
{
int lo = (i * k) - 1;
int hi = Math.Min(maxVal, (k + 1) * i - 1); // [i*k, i*(k+1) -1]
int count = prefixSums[hi] - prefixSums[lo];
ans = (ans + 1L * freq[i] * k * count) % mod;
}
}
return (int)ans;
}
}