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Print k different sorted permutations of a given array in C Program.
Given an array a[] containing N integers, the challenge is to print k different permutations of indices such that the values at those indices form a non-decreasing sequence. Print -1 if it is not possible.
Example
Input: arr[] = {2,5,6,2,2,2,2}, k = 4
Output:
0 3 4 5 6 1 2
3 0 4 5 6 1 2
0 3 4 5 6 1 2
3 0 4 5 6 1 2Sort the given array and keep track of the original indices of each element. That gives one required permutation. Now if any 2 continuous elements are equal then they can be swapped to get another permutation. Similarly, the third permutation can be generated.
Algorithm
START
Step 1 -> Declare Function void indice(int n, pair<int, int> array[])
Loop For int i=0 and i<n and i++
Print array[i].second
End
Step 2 -> Declare Function void permutation(int n, int a[], int k)
Use STL pair<int, int> arr[n]
Loop for int i=0 and i<n and i++
Set arr[i].first = a[i]
Set arr[i].second = i
End
Call sort(arr, arr + n)
Declare int count to 1
Loop For int i=1 and i<n and i++
IF (arr[i].first == arr[i - 1].first)
Increment count by 1
End
End
IF count < k
Return -1
End
Loop For int i = 0 and i < k – 1 and i++
Call indice(n, arr)
Loop For int j = 1 and j < n and j++
IF arr[j].first == arr[j - 1].first
Call swap(arr[j], arr[j - 1])
Break
End
End
End
Call indice(n, arr)
Step 3 -> In main()
Declare array a[]={2,5,6,2,2,2,2}
Declare int n= sizeof(a)/sizeof(a[0])
Declare int k=4
Call permutation(n,a,k)
STOPExample
#include <bits/stdc++.h>
using namespace std;
void indice(int n, pair<int, int> array[]){
for (int i = 0; i < n; i++)
cout << array[i].second << " ";
cout << endl;
}
void permutation(int n, int a[], int k){
pair<int, int> arr[n];
for (int i = 0; i < n; i++){
arr[i].first = a[i];
arr[i].second = i;
}
sort(arr, arr + n);
int count = 1;
for (int i = 1; i < n; i++)
if (arr[i].first == arr[i - 1].first)
count++;
if (count < k){
cout << "-1";
return;
}
for (int i = 0; i < k - 1; i++){
indice(n, arr);
for (int j = 1; j < n; j++){
if (arr[j].first == arr[j - 1].first){
swap(arr[j], arr[j - 1]);
break;
}
}
}
indice(n, arr);
}
int main(){
int a[] ={2,5,6,2,2,2,2};
int n = sizeof(a) / sizeof(a[0]);
int k = 4;
permutation(n, a, k);
return 0;
}Output
if we run above program then it will generate following output
0 3 4 5 6 1 2 3 0 4 5 6 1 2 0 3 4 5 6 1 2 3 0 4 5 6 1 2
Updated on: 22-Aug-2019
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