Sort the character array based on ASCII % N
Given an array arr[] of characters and an integer M, the task is to sort the array based on ASCII % M i.e. the character whose ASCII value % M is minimum should appear first.
Examples:
Input: arr[] = {‘a’, ‘b’, ‘c’, ‘e’}, M = 2
Output: b a c e
The ASCII % M for the array are
{97 % 2, 98 % 2, 99 % 2, 101 % 2} i.e. {1, 0, 1, 1}
Input: arr[] = {‘g’, ‘e’, ‘e’, ‘k’, ‘s’}, M = 8
Output: k s e e g
Method 1: Write a function to sort the array and instead of comparing the values of the characters, compare their ASCII values % M to sort the array. Print the sorted array in the end.
Below is the implementation of the above approach:
C++
// C++ implementation of the approach #include <bits/stdc++.h> using namespace std; // A utility function to swap two elements void swap(char* a, char* b) { char t = *a; *a = *b; *b = t; } /* This function takes last element as pivot, places the pivot element at its correct position in sorted array, and places all smaller (smaller than pivot) to left of pivot and all greater elements to right of pivot */int partition(char arr[], int low, int high, int mod) { // pivot char pivot = arr[high]; // Index of smaller element int i = (low - 1); int piv = pivot % mod; for (int j = low; j <= high - 1; j++) { int a = arr[j] % mod; // If current element is smaller than or // equal to pivot // Instead of values, ASCII % m values // are compared if (a <= piv) { // Increment index of smaller element i++; swap(&arr[i], &arr[j]); } } swap(&arr[i + 1], &arr[high]); return (i + 1); } /* The main function that implements QuickSort arr[] --> Array to be sorted, low --> Starting index, high --> Ending index */void quickSort(char arr[], int low, int high, int mod) { if (low < high) { /* pi is partitioning index, arr[p] is now at right place */ int pi = partition(arr, low, high, mod); // Separately sort elements before // partition and after partition quickSort(arr, low, pi - 1, mod); quickSort(arr, pi + 1, high, mod); } } // Function to print the given array void printArray(char arr[], int size) { for (int i = 0; i < size; i++) cout << arr[i] << " "; } // Driver code int main() { char arr[] = { 'g', 'e', 'e', 'k', 's' }; int n = sizeof(arr) / sizeof(arr[0]); int mod = 8; // Sort the given array quickSort(arr, 0, n - 1, mod); // Print the sorted array printArray(arr, n); return 0; } |
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Java
// Java implementation of the approach class GFG { /* This function takes last element as pivot, places the pivot element at its correct position in sorted array, and places all smaller (smaller than pivot) to left of pivot and all greater elements to right of pivot */ static int partition(char arr[], int low, int high, int mod) { // pivot char pivot = arr[high]; // Index of smaller element int i = (low - 1); int piv = pivot % mod; for (int j = low; j <= high - 1; j++) { int a = arr[j] % mod; // If current element is smaller than or // equal to pivot // Instead of values, ASCII % m values // are compared if (a <= piv) { // Increment index of smaller element i++; // swap char t = arr[i]; arr[i] = arr[j]; arr[j] = t; } } char t = arr[i+1]; arr[i+1] = arr[high]; arr[high] = t; return (i + 1); } /* The main function that implements QuickSort arr[] --> Array to be sorted, low --> Starting index, high --> Ending index */ static void quickSort(char arr[], int low, int high, int mod) { if (low < high) { /* pi is partitioning index, arr[p] is now at right place */ int pi = partition(arr, low, high, mod); // Separately sort elements before // partition and after partition quickSort(arr, low, pi - 1, mod); quickSort(arr, pi + 1, high, mod); } } // Function to print the given array static void printArray(char arr[], int size) { for (int i = 0; i < size; i++) System.out.print(arr[i] + " "); } // Driver code public static void main(String [] args) { char arr[] = { 'g', 'e', 'e', 'k', 's' }; int n = arr.length; int mod = 8; // Sort the given array quickSort(arr, 0, n - 1, mod); // Print the sorted array printArray(arr, n); } } // This code is contibuted by ihritik |
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C#
// C# implementation of the approach using System; class GFG { /* This function takes last element as pivot, places the pivot element at its correct position in sorted array, and places all smaller (smaller than pivot) to left of pivot and all greater elements to right of pivot */ static int partition(char []arr, int low, int high, int mod) { // pivot char pivot = arr[high]; // Index of smaller element int i = (low - 1); char t; int piv = pivot % mod; for (int j = low; j <= high - 1; j++) { int a = arr[j] % mod; // If current element is smaller than o // equal to pivot // Instead of values, ASCII % m values // are compared if (a <= piv) { // Increment index of smaller element i++; // swap t = arr[i]; arr[i] = arr[j]; arr[j] = t; } } t = arr[i+1]; arr[i+1] = arr[high]; arr[high] = t; return (i + 1); } /* The main function that implements QuickSort arr[] --> Array to be sorted, low --> Starting index, high --> Ending index */ static void quickSort(char []arr, int low, int high, int mod) { if (low < high) { /* pi is partitioning index, arr[p] is now at right place */ int pi = partition(arr, low, high, mod); // Separately sort elements before // partition and after partition quickSort(arr, low, pi - 1, mod); quickSort(arr, pi + 1, high, mod); } } // Function to print the given array static void printArray(char []arr, int size) { for (int i = 0; i < size; i++) Console.Write(arr[i] + " "); } // Driver code public static void Main() { char []arr = { 'g', 'e', 'e', 'k', 's' }; int n = arr.Length; int mod = 8; // Sort the given array quickSort(arr, 0, n - 1, mod); // Print the sorted array printArray(arr, n); } } // This code is contibuted by ihritik |
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Python3
# Python3 implementation of the above approach """ This function takes last element as pivot, places the pivot element at its correct position in sorted array, and places all smaller (smaller than pivot) to left of pivot and all greater elements to right of pivot """def partition(arr, low, high, mod) : # pivot pivot = ord(arr[high]); # Index of smaller element i = (low - 1); piv = pivot % mod; for j in range(low, high) : a = ord(arr[j]) % mod; # If current element is smaller than or # equal to pivot # Instead of values, ASCII % m values # are compared if (a <= piv) : # Increment index of smaller element i += 1; arr[i], arr[j] = arr[j], arr[i] arr[i + 1], arr[high] = arr[high], arr[i + 1] return (i + 1); """ The main function that implements QuickSort arr[] --> Array to be sorted, low --> Starting index, high --> Ending index """ def quickSort(arr, low, high, mod) : if (low < high) : ''' pi is partitioning index, arr[p] is now at right place ''' pi = partition(arr, low, high, mod); # Separately sort elements before # partition and after partition quickSort(arr, low, pi - 1, mod); quickSort(arr, pi + 1, high, mod); return arr # Function to print the given array def printArray(arr, size) : for i in range(0, size) : print(arr[i], end = " "); # Driver code if __name__ == "__main__" : arr = [ 'g', 'e', 'e', 'k', 's' ]; n = len(arr); mod = 8; # Sort the given array arr = quickSort(arr, 0, n - 1, mod); # Print the sorted array printArray(arr, n); # This code is contributed by AnkitRai01 |
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Output:
k s e e g
Method 2: The sorting can also be done using std::sort() and modifying the comparator.
Below is the implementation of the above approach:
// C++ implementation of the approach #include <bits/stdc++.h> using namespace std; int M; // Comparator used to sort the array // according to ASCII % M bool comparator(char ch1, char ch2) { int i = ch1 % M; int j = ch2 % M; return (i < j); } // Function to print the given array void printArray(char arr[], int size) { for (int i = 0; i < size; i++) cout << arr[i] << " "; } // Driver code int main() { char arr[] = { 'g', 'e', 'e', 'k', 's' }; int n = sizeof(arr) / sizeof(arr[0]); M = 8; // Sort the given array sort(arr, arr + n, comparator); // Print the sorted array printArray(arr, n); return 0; } |
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Output:
k s e e g
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