Insertion Sort Advanced Analysis
Problem Statement :
Insertion Sort is a simple sorting technique which was covered in previous challenges. Sometimes, arrays may be too large for us to wait around for insertion sort to finish. Is there some other way we can calculate the number of shifts an insertion sort performs when sorting an array? Function description Complete the insertionSort function in the editor below. insertionSort has the following parameter(s): int arr[n]: an array of integers Returns - int: the number of shifts required to sort the array Input Format The first line contains a single integer t, the number of queries to perform. The following t pairs of lines are as follows: The first line contains an integer n, the length of arr. The second line contains n space-separated integers arr[i]. Constraints 1 <= t <= 15 1 <= n <= 100000 1 <= arr[i] <= 10000000
Solution :
Solution in C :
In C++ :
#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std ;
#define MAXN 100002
#define MAX 1000002
int n,a[MAXN],c[MAX] ;
int main()
{
int runs ;
scanf("%d",&runs) ;
while(runs--)
{
scanf("%d",&n) ;
for(int i = 0;i < n;i++) scanf("%d",&a[i]) ;
long long ret = 1LL * n * (n - 1) / 2 ;
memset(c,0,sizeof c) ;
for(int i = 0;i < n;i++)
{
for(int j = a[i];j > 0;j -= j & -j) ret -= c[j] ;
for(int j = a[i];j < MAX;j += j & -j) c[j]++ ;
}
cout << ret << endl ;
}
return 0 ;
}
In Java :
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
public class Solution
{
public static void main(String[] args) throws Exception
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int T,N,t,j;
int[] nums;
T = Integer.parseInt(br.readLine());
for (t = 0; t < T; t++)
{
N = Integer.parseInt(br.readLine());
nums = new int[N];
String[] strs = br.readLine().split(" ");
for (j = 0; j < N; j++)
nums[j] = Integer.parseInt(strs[j]);
System.out.print(Long.toString(sort_and_count(nums, 0, N - 1))+"\n");
}
}
public static long sort_and_count(int[] a, int x1, int x2)
{
if (x2 <= x1)
return 0L;
if (x2 == x1 + 1)
{
if (a[x1] > a[x2])
{
a[x1] ^= a[x2];
a[x2] ^= a[x1];
a[x1] ^= a[x2];
return 1L;
}
return 0L;
}
int mid = (x2 + x1) / 2;
long count = 0L;
count += sort_and_count(a, x1, mid);
count += sort_and_count(a, mid + 1, x2);
count += merge_and_count(a, x1, mid, mid + 1, x2);
return count;
}
public static long merge_and_count(int[] a, int x1, int x2, int y1, int y2)
{
long count = 0L;
for (int i = x1, j = y1; i <= x2 && j <= y2;)
{
if (a[i] > a[j])
{
count += (long) (x2 - i + 1);
j++;
}
else
i++;
}
Arrays.sort(a, x1, y2 + 1);
return count;
}
public static long insertSort(int[] a)
{
long count = 0;
int i,j;
for (i = 1; i < a.length; i++)
{
j = i;
while (j >= 1 && a[j] < a[j - 1])
{
a[j] ^= a[j - 1];
a[j - 1] ^= a[j];
a[j] ^= a[j - 1];
count++;
j--;
}
}
return count;
}
}
In C :
#include<stdio.h>
unsigned long long int cnt;
int main()
{
int *p,t,i,n;
scanf("%d",&t);
while(t--)
{
cnt=0;
scanf("%d",&n);
p=(int*)malloc(sizeof(int)*n);
for(i=0;i<n;i++)
scanf("%d",&p[i]);
merge(p,0,n-1);
printf("%llu\n",cnt);
}
return 0;
}
int merge(int *p,int l,int h)
{
int m;
if(l<h)
{
m=(l+h)/2;
merge(p,l,m);
merge(p,m+1,h);
sort(p,l,m,h);
}
}
int sort(int *p,int l,int m,int h)
{
int i=l,j=m+1,n=0,*k;
k=(int *)malloc(sizeof(int)*(h-l+1));
while(i<=m&&j<=h)
{
if(p[i]<=p[j])
k[n++]=p[i++];
else
{
cnt+=(m-i+1);
k[n++]=p[j++];
}
}
while(i<=m)
k[n++]=p[i++];
while(j<=h)
k[n++]=p[j++];
for(i=0;i<(h-l+1);i++)
p[l+i]=k[i];
}
In Python3 :
def mergeSort(m):
if len(m) <= 1:
return [0, m]
mid = len(m)//2
l = []
r = []
for i in range(mid):
l.append(m[i])
for i in range(mid, len(m)):
r.append(m[i])
left = mergeSort(l)
right = mergeSort(r)
return merge(left, right)
def merge(left, right):
i = 0
j = 0
result = []
num = left[0] + right[0]
while i < len(left[1]) or j < len(right[1]):
if i < len(left[1]) and j < len(right[1]):
if left[1][i] <= right[1][j]:
result.append(left[1][i])
i += 1
num += j
else:
result.append(right[1][j])
j += 1
elif i < len(left[1]):
result.append(left[1][i])
i += 1
num += j
elif j < len(right[1]):
result.append(right[1][j])
j += 1
return [num, result]
T = int(input())
for i in range(T):
n = int(input())
nums = [int(i) for i in input().split()]
print(mergeSort(nums)[0])
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