CODESPTB - Insertion Sort
Insertion Sort is a classical sorting technique. One variant of insertion sort works as follows when sorting an array a[1..N] in non-descending order:
for i <- 2 to N j <- i while j > 1 and a[j] < a[j - 1] swap a[j] and a[j - 1] j <- j - 1
The pseudocode is simple to follow. In the ith step, element a[i] is inserted in the sorted sequence a[1..i - 1]. This is done by moving a[i] backward by swapping it with the previous element until it ends up in it's right position.
As you probably already know, the algorithm can be really slow. To study this more, you want to find out the number of times the swap operation is performed when sorting an array.
The first line contains the number of test cases T. T test cases follow. The first line for each case contains N, the number of elements to be sorted. The next line contains N integers a,a...,a[N].
Output T lines, containing the required answer for each test case.
1 <= T <= 5
1 <= N <= 100000
1 <= a[i] <= 1000000
Sample Input: 2 5 1 1 1 2 2 5 2 1 3 1 2 Sample Output: 0 4
easy.just apply BIT
Basic insertion sort with counter at each swap works.
just count the inversions in the array.....using bit or segment tree
This question screams merge sort tree, though you don't have to create the whole tree. Just sorting would do.
BIT was much faster than mergesort trick , and be careful with \n at the end. it costed me many WA's :)
Solved using BIT :)
Test cases are weak
policy based data structure! but the time limit needs to be improves even a brute force insertion sort passes!Last edit: 2016-09-14 17:00:43
I'm just a novice solver but through my perspective, Mitch is right.
The other problem that everyone refers to has a somewhat different problem statement, and I think it would not be obvious to many that they are equivalent if not for the comments. So a case can be made that they are spoilers and should be censored. Opinions?