|632|[Smallest Range](https://leetcode.com/problems/smallest-range/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_632.java) | O(n*logk) |O(k) | Hard| Heap

|631|[Design Excel Sum Formula](https://leetcode.com/problems/design-excel-sum-formula/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_631.java) | | | Hard| Design, Topological Sort

|630|[Course Schedule III](https://leetcode.com/problems/course-schedule-iii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_630.java) | O(n*logn) |O(n) | Hard| Heap, Greedy

|629|[K Inverse Pairs Array](https://leetcode.com/problems/k-inverse-pairs-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_629.java) | O(n*k) |O(n*k) | Hard| DP

|628|[Maximum Product of Three Numbers](https://leetcode.com/problems/maximum-product-of-three-numbers/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_628.java)| O(nlogn)|O(1)| Easy|

|625|[Minimum Factorization](https://leetcode.com/problems/minimum-factorization/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_625.java)| O(?)|O(?)| Medium|

|624|[Maximum Distance in Arrays](https://leetcode.com/problems/maximum-distance-in-arrays/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_624.java) | O(nlogn) |O(1) | Easy | Sort, Array

publicclass_629 {

publicintkInversePairs(intn,intk) {

return0;

intmod =1000000007;

if (k >n*(n-1)/2 ||k <0)return0;

if (k ==0 ||k ==n*(n-1)/2)return1;

long[][]dp =newlong[n+1][k+1];

dp[2][0] =1;

dp[2][1] =1;

for (inti =3;i <=n;i++) {

dp[i][0] =1;

for (intj =1;j <=Math.min(k,i*(i-1)/2);j++) {

dp[i][j] =dp[i][j-1] +dp[i-1][j];

if (j >=i)dp[i][j] -=dp[i-1][j-i];

dp[i][j] = (dp[i][j]+mod) %mod;

}

}

return (int)dp[n][k];

}

}