Given an array of integers, determine whether the array can be sorted in ascending order using only one of the following operations one time.
- Swap two elements.
- Reverse one sub-segment.
Determine whether one, both or neither of the operations will complete the task. If both work, choose swap. For instance, given an array [2,3,5,4] either swap the 4 and 5, or reverse them to sort the array. Choose swap. The Output Format section below details requirements.
Function Description
Complete the almostSorted function in the editor below. It should print the results and return nothing.
almostSorted has the following parameter(s):
arr: an array of integers
Input Format
The first line contains a single integer n, the size of arr.
The next line contains n space-separated integers arr[i] where 1<=i<=n.
Output Format
If the array is already sorted, output yes on the first line. You do not need to output anything else.
2. If you can sort this array using one single operation (from the two permitted operations) then output yes on the first line and then:
a. If elements can be swapped,d[l] and d[r], output swap l r in the second line.l and r are the indices of the elements to be swapped, assuming that the array is indexed from 1 to n.
b. Otherwise, when reversing the segment d[l…r], output reverse l r in the second line.l and r are the indices of the first and last elements of the subsequence to be reversed, assuming that the array is indexed from 1 to n.
d[l…r] represents the sub-sequence of the array, beginning at index and ending at index , both inclusive.
If an array can be sorted by either swapping or reversing, choose swap.
If you cannot sort the array either way, output no on the first line.
Sample Input 1
2 4 2
Sample Output 1
yes swap 1 2
Explanation 1
You can either swap(1, 2) or reverse(1, 2). You prefer swap.
Sample Input 2
3
3 1 2
Sample Output 2
no
Explanation 2
It is impossible to sort by one single operation.
Sample Input 3
6
1 5 4 3 2 6
Sample Output 3
yes
reverse 2 5
Explanation 3
You can reverse the sub-array d[2…5] = “5 4 3 2”, then the array becomes sorted.
Almost Sorted HackerRank Solution in C
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <limits.h>
int n;
int v[100002];
int l, r;
int issorted() {
for (int i = 1; i <= n; i++)
if (v[i-1] > v[i])
return 0;
return 1;
}
int testreverse() {
int i;
int first;
for (i = 1; i <= n; i++) {
if (v[i-1] > v[i]) {
first = i;
break;
}
}
if (i == n+1) return 0; // sorted!
int second;
for (i = first+1; i <= n; i++) {
if (v[i-1] < v[i]) {
second = i;
break;
}
}
if (i == n+1) {
l = first - 1;
r = n;
return (v[n] >= v[first-2]);
}
// Rest sorted?
for (i = second+1; i <= n; i++) {
if (v[i-1] > v[i])
return 0;
}
l = first - 1;
r = second - 1;
return (v[first-1] <= v[second] && v[second-1] >= v[first-2]);
}
int testswap() {
int i;
int first;
for (i = 1; i <= n; i++) {
if (v[i-1] > v[i]) {
first = i;
break;
}
}
if (i == n+1) return 0; // sorted!
if (v[first-2] > v[first]) {
return 0;
}
int second;
for (i = first+1; i <= n; i++) {
if (v[i-1] > v[i]) {
second = i;
break;
}
}
if (i == n+1) {
return 0;
}
// Rest sorted?
for (i = second+1; i <= n; i++) {
if (v[i-1] > v[i])
return 0;
}
// l = first - 1;
// r = second - 1;
// return (v[first-1] <= v[second] && v[second-1] >= v[first-2]);
l = first - 1;
r = second;
return (v[l-1] <= v[r] && v[r] <= v[l+1] && v[r-1] <= v[l] && v[l] <= v[r+1]);
}
int main() {
int stage = 0;
scanf("%d", &n);
for (int i = 0; i < n; i++)
scanf("%d", &v[i+1]);
v[0] = INT_MIN;
v[n+1] = INT_MAX;
int first;
// Sorted?
if (issorted()) {
printf("yes\n");
return 0;
}
if (testreverse()) {
int i;
for (i = l; i < r; i++) if (v[l] != v[i]) break;
if (i == r)
printf("yes\nswap %d %d", l, r);
else
printf("yes\nreverse %d %d", l, r);
return 0;
}
if (testswap()) {
printf("yes\nswap %d %d", l, r);
return 0;
}
printf("no");
}
Almost Sorted HackerRank Solution in C++
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <algorithm>
#include <iostream>
using namespace std;
int N, v[100005], s[100005];
int main() {
cin >> N;
for(int i=0; i<N; i++){
cin >> v[i];
s[i] = v[i];
}
sort(s, s+N);
vector<int> diff;
for(int i=0; i<N; i++)
if(v[i] != s[i])
diff.push_back(i);
if(diff.size() == 0){
cout << "yes" << endl;
return 0;
}
if(diff.size() == 2 && s[diff[0]] == v[diff[1]] && s[diff[1]] == v[diff[0]]){
cout << "yes\nswap " << diff[0] + 1 << " " << diff[1] + 1 << endl;
return 0;
}
reverse(v + diff[0], v + diff.back() + 1);
bool good = true;
for(int i=0; i<N; i++)
good &= v[i] == s[i];
if(good) cout << "yes\nreverse " << diff[0] + 1 << " " << diff.back() + 1 << endl;
else cout << "no" << endl;
return 0;
}
Almost Sorted HackerRank Solution in Java
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashMap;
public class Solution {
private static Reader in;
private static PrintWriter out;
public static void main(String[] args) throws IOException {
in = new Reader();
out = new PrintWriter(System.out, true);
int N = in.nextInt();
int[] arr = new int[N];
for (int i = 0; i < N; i++)
arr[i] = in.nextInt();
int[] brr = Arrays.copyOf(arr, N);
Arrays.sort(brr);
HashMap<Integer, Integer> mp = new HashMap<Integer, Integer>();
for (int i = 0; i < N; i++)
mp.put(brr[i], i);
for (int i = 0; i < N; i++) {
arr[i] = mp.get(arr[i]);
}
int outofpos = 0;
for (int i = 0; i < N; i++) {
if (arr[i] != i)
outofpos++;
}
if (outofpos == 0) {
out.println("yes");
out.close();
System.exit(0);
} else if (outofpos == 2) {
out.println("yes");
out.print("swap");
for (int i = 0; i < N; i++) {
if (arr[i] != i)
out.print(" " + (i + 1));
}
out.println();
out.close();
System.exit(0);
} else {
int s = -1, e = -1;
for (int i = 0; i < N; i++) {
if (arr[i] != i) {
e = i;
if (s == -1) s = i;
}
}
for (int i = s, j = e; i < j; i++, j--) {
int t = arr[i]; arr[i] = arr[j]; arr[j] = t;
}
for (int i = 0; i < N; i++) {
if (arr[i] != i) {
out.println("no");
out.close();
System.exit(0);
}
}
out.println("yes");
out.printf("reverse %d %d\n", s+1, e+1);
out.close();
System.exit(0);
}
out.close();
System.exit(0);
}
static class Reader {
final private int BUFFER_SIZE = 1 << 16;
private DataInputStream din;
private byte[] buffer;
private int bufferPointer, bytesRead;
public Reader() {
din = new DataInputStream(System.in);
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public Reader(String file_name) throws IOException {
din = new DataInputStream(new FileInputStream(file_name));
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public String readLine() throws IOException {
byte[] buf = new byte[1024];
int cnt = 0, c;
while ((c = read()) != -1) {
if (c == '\n')
break;
buf[cnt++] = (byte) c;
}
return new String(buf, 0, cnt);
}
public int nextInt() throws IOException {
int ret = 0;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public long nextLong() throws IOException {
long ret = 0;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public double nextDouble() throws IOException {
double ret = 0, div = 1;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (c == '.')
while ((c = read()) >= '0' && c <= '9')
ret += (c - '0') / (div *= 10);
if (neg)
return -ret;
return ret;
}
private void fillBuffer() throws IOException {
bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
if (bytesRead == -1)
buffer[0] = -1;
}
private byte read() throws IOException {
if (bufferPointer == bytesRead)
fillBuffer();
return buffer[bufferPointer++];
}
public void close() throws IOException {
if (din == null)
return;
din.close();
}
}
}
Almost Sorted HackerRank Solution in Python
def mismatch(A):
B = list(sorted(A))
return [i for i in xrange(len(A)) if A[i]!=B[i]]
def swappable(A, indices):
return len(indices)==2
def reversible(A, indices):
minimum = min(indices)
maximum = max(indices)
B = A[minimum:maximum+1][::-1]
if B == list(sorted(B)):
return minimum,maximum
return False
N = int(raw_input())
A = [-1] + map(int, raw_input().split())
I = mismatch(A)
if swappable(A,I):
print "yes\nswap %d %d"%(I[0],I[1])
else:
R = reversible(A,I)
if R:
print 'yes\nreverse %d %d'%(R[0],R[1])
else:
print 'no'
Almost Sorted HackerRank Solution in C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace AlmostSorted
{
class Program
{
static void Main(string[] args)
{
int n = int.Parse(Console.ReadLine());
int[] arr = new int[n];
string[] split = Console.ReadLine().Split(' ');
for (int i = 0; i < n; i++)
{
arr[i] = int.Parse(split[i]);
}
int s = 1;
while (s < n && arr[s] >= arr[s - 1])
{
s++;
}
if (s == n)
{
Console.WriteLine("yes");
return;
}
int e = n - 2;
while (e >= 0 && arr[e] <= arr[e + 1])
{
e--;
}
s--;
e++;
// Lets try swapping
int temp = arr[s];
arr[s] = arr[e];
arr[e] = temp;
if (s > 0 && arr[s] < arr[s - 1])
{
Console.WriteLine("no");
return;
}
if (e < n - 1 && arr[e] > arr[e + 1])
{
Console.WriteLine("no");
return;
}
// Is it assending from s to e?
bool isAscending = true;
for (int i = s + 1; i <= e; i++)
{
if (arr[i] < arr[i - 1])
{
isAscending = false;
break;
}
}
if (isAscending)
{
Console.WriteLine("yes");
Console.WriteLine("swap {0} {1}", s+1, e+1);
return;
}
// Lets try reverse
temp = arr[s];
arr[s] = arr[e];
arr[e] = temp;
isAscending = true;
for (int i = e - 1; i >= s; i--)
{
if (arr[i] < arr[i + 1])
{
isAscending = false;
break;
}
}
if (isAscending)
{
Console.WriteLine("yes");
Console.WriteLine("reverse {0} {1}", s + 1, e + 1);
return;
}
Console.WriteLine("no");
}
}
}
Attempt Almost Sorted HackerRank Challenge
Link – https://www.hackerrank.com/challenges/almost-sorted/
Next HackerRank Challenge Solution
Link – https://exploringbits.com/matrix-layer-rotation-hackerrank-solution/
Aayush Kumar Gupta is the founder and creator of ExploringBits, a website dedicated to providing useful content for people passionate about Engineering and Technology. Aayush has completed his Bachelor of Technology (Computer Science & Engineering) from 2018-2022. From July 2022, Aayush has been working as a full-time Devops Engineer.
