Find all permuted rows of a given row in a matrix

We are given a m*n matrix of positive integers and a row number. The task is to find all rows in given matrix which are permutations of given row elements. It is also given that values in every row are distinct.

Examples:

```Input : mat[][] = {{3, 1, 4, 2},
{1, 6, 9, 3},
{1, 2, 3, 4},
{4, 3, 2, 1}}
row = 3
Output: 0, 2
Rows at indexes 0 and 2 are permutations of
row at index 3.
```

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

A simple solution is to one by one sort all rows and check all rows. If any row is completely equal to given row that means current row is a permutation of given row. Time complexity for this approach will be O(m*n log n).

An efficient approach is to use a hashing. Simply create a hash set for given row. After hash set creation, traverse through remaining rows and for every row check if all of its elements are present in hash set or not.

CPP

 `// C++ program to find all permutations of a given row ` `#include ` `#define MAX 100 ` ` `  `using` `namespace` `std; ` ` `  `// Function to find all permuted rows of a given row r ` `void` `permutatedRows(``int` `mat[][MAX], ``int` `m, ``int` `n, ``int` `r) ` `{ ` `    ``// Creating an empty set ` `    ``unordered_set<``int``> s; ` ` `  `    ``// Count frequencies of elements in given row r ` `    ``for` `(``int` `j=0; j

Java

 `// Java program to find all permutations of a given row ` `import` `java.util.*; ` ` `  `class` `GFG ` `{ ` `     `  `static` `int` `MAX = ``100``; ` ` `  `// Function to find all permuted rows of a given row r ` `static` `void` `permutatedRows(``int` `mat[][], ``int` `m, ``int` `n, ``int` `r) ` `{ ` `    ``// Creating an empty set ` `    ``LinkedHashSet s = ``new` `LinkedHashSet<>(); ` ` `  ` `  `    ``// Count frequencies of elements in given row r ` `    ``for` `(``int` `j = ``0``; j < n; j++) ` `        ``s.add(mat[r][j]); ` ` `  `    ``// Traverse through all remaining rows ` `    ``for` `(``int` `i = ``0``; i < m; i++) ` `    ``{ ` `        ``// we do not need to check for given row r ` `        ``if` `(i == r) ` `            ``continue``; ` ` `  `        ``// initialize hash i.e; count frequencies ` `        ``// of elements in row i ` `        ``int` `j; ` `        ``for` `(j = ``0``; j < n; j++) ` `            ``if` `(!s.contains(mat[i][j])) ` `                ``break``; ` `        ``if` `(j != n) ` `        ``continue``; ` ` `  `        ``System.out.print(i+``", "``); ` `    ``} ` `} ` ` `  `// Driver program to run the case ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``int` `m = ``4``, n = ``4``,r = ``3``; ` `    ``int` `mat[][] = {{``3``, ``1``, ``4``, ``2``}, ` `                    ``{``1``, ``6``, ``9``, ``3``}, ` `                    ``{``1``, ``2``, ``3``, ``4``}, ` `                    ``{``4``, ``3``, ``2``, ``1``}}; ` `    ``permutatedRows(mat, m, n, r); ` `} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

Python3

 `# Python program to find all ` `# permutations of a given row ` ` `  `# Function to find all ` `# permuted rows of a given row r ` `def` `permutatedRows(mat, m, n, r): ` ` `  ` `  `    ``# Creating an empty set ` `    ``s``=``set``() ` ` `  `    ``# Count frequencies of ` `    ``# elements in given row r ` `    ``for` `j ``in` `range``(n): ` `        ``s.add(mat[r][j])     ` ` `  `    ``# Traverse through all remaining rows ` `    ``for` `i ``in` `range``(m): ` ` `  `        ``# we do not need to check ` `        ``# for given row r ` `        ``if` `i ``=``=` `r: ` `            ``continue` ` `  `        ``# initialize hash i.e ` `        ``# count frequencies ` `        ``# of elements in row i ` `        ``for` `j ``in` `range``(n): ` `            ``if` `mat[i][j] ``not` `in` `s: ` ` `  `                ``# to avoid the case when last ` `                ``# element does not match ` `                ``j ``=` `j ``-` `2` `                ``break``; ` `        ``if` `j ``+` `1` `!``=` `n: ` `            ``continue` `        ``print``(i) ` `             `  `     `  ` `  `# Driver program to run the case ` `m ``=` `4` `n ``=` `4` `r ``=` `3` `mat ``=` `[[``3``, ``1``, ``4``, ``2``], ` `       ``[``1``, ``6``, ``9``, ``3``], ` `       ``[``1``, ``2``, ``3``, ``4``], ` `       ``[``4``, ``3``, ``2``, ``1``]] ` ` `  `permutatedRows(mat, m, n, r) ` ` `  `# This code is contributed ` `# by Upendra Singh Bartwal. `

C#

 `// C# program to find all permutations of a given row  ` `using` `System; ` `using` `System.Collections.Generic; ` ` `  `class` `GFG  ` `{  ` `     `  `static` `int` `MAX = 100;  ` ` `  `// Function to find all permuted rows of a given row r  ` `static` `void` `permutatedRows(``int` `[,]mat, ``int` `m, ``int` `n, ``int` `r)  ` `{  ` `    ``// Creating an empty set  ` `    ``HashSet<``int``> s = ``new` `HashSet<``int``>();  ` ` `  ` `  `    ``// Count frequencies of elements in given row r  ` `    ``for` `(``int` `j = 0; j < n; j++)  ` `        ``s.Add(mat[r, j]);  ` ` `  `    ``// Traverse through all remaining rows  ` `    ``for` `(``int` `i = 0; i < m; i++)  ` `    ``{  ` `        ``// we do not need to check for given row r  ` `        ``if` `(i == r)  ` `            ``continue``;  ` ` `  `        ``// initialize hash i.e; count frequencies  ` `        ``// of elements in row i  ` `        ``int` `j;  ` `        ``for` `(j = 0; j < n; j++)  ` `            ``if` `(!s.Contains(mat[i,j]))  ` `                ``break``;  ` `        ``if` `(j != n)  ` `        ``continue``;  ` ` `  `        ``Console.Write(i+``", "``);  ` `    ``}  ` `}  ` ` `  `// Driver program to run the case  ` `public` `static` `void` `Main(String[] args)  ` `{  ` `    ``int` `m = 4, n = 4,r = 3;  ` `    ``int` `[,]mat = {{3, 1, 4, 2},  ` `                    ``{1, 6, 9, 3},  ` `                    ``{1, 2, 3, 4},  ` `                    ``{4, 3, 2, 1}};  ` `    ``permutatedRows(mat, m, n, r);  ` `}  ` `}  ` ` `  `/* This code contributed by PrinciRaj1992 */`

Output:

```0, 2
```

Time complexity : O(m*n)
Auxiliary space : O(n)

Another approach to the solution using Standard Template Library(STL):

CPP

 `// C++ program to find all permutations of a given row ` `#include ` `#define MAX 100 ` ` `  `using` `namespace` `std; ` ` `  `// Function to find all permuted rows of a given row r ` `void` `permutatedRows(``int` `mat[][MAX], ``int` `m, ``int` `n, ``int` `r) ` `{ ` `   ``for` `(``int` `i=0; i

Output:

```0, 2
```

Exercise :
Extend the above solution to work for input matrix where all elements of a row don’t have be distinct. (Hit : We can use Hash Map instead of Hash Set)

tags:

Hash Matrix Hash Matrix