Suppose we have a string with n elements (n < 10). We have to find the number of ways that the string can be arranged without changing the relative position of the vowel and consonants.
The approach is simple. We have to count the number of vowels and consonants in the given string, then we have to find how many ways we can arrange the vowels only, then find the number of ways to arrange the consonant only, after that multiply these two results to get the total ways.
Algorithm
arrangeWayCount(str)
Begin define an array ‘freq’ to store frequency. count and place frequency of each characters in freq array. such that freq[‘0’] will hold frequency of letter ‘a’, freq[1] will hold frequency of ‘b’ and so on. v := number of vowels, and c := number of consonants in str vArrange := factorial of v for each vowel v in [a, e, i, o, u], do vArrange := vArrange / factorial of the frequency of v done cArrange := factorial of c for each consonant con, do cArrange := cArrange / factorial of the frequency of con done return vArrange * cArrange End
Example
#include <iostream> using namespace std; long long factorial(int n){ if(n == 0 || n == 1) return 1; return n*factorial(n-1); } long long arrangeWayCount(string str){ long long freq[27] = {0}; //fill frequency array to 0 int v = 0, c = 0; for (int i = 0; i < str.length(); i++) { freq[str[i] - 'a']++; if (str[i] == 'a' || str[i] == 'e' || str[i] == 'i' || str[i] == 'o' || str[i] == 'u') { v++; }else c++; } long long arrangeVowel; arrangeVowel = factorial(v); arrangeVowel /= factorial(freq[0]); // vowel a arrangeVowel /= factorial(freq[4]); // vowel e arrangeVowel /= factorial(freq[8]); // vowel i arrangeVowel /= factorial(freq[14]); // vowel o arrangeVowel /= factorial(freq[20]); // vowel u long long arrangeConsonant; arrangeConsonant = factorial(c); for (int i = 0; i < 26; i++) { if (i != 0 && i != 4 && i != 8 && i != 14 && i != 20) arrangeConsonant /= factorial(freq[i]); //frequency of all characters except vowels } long long total = arrangeVowel * arrangeConsonant; return total; } main() { string str = "computer"; long long ans = arrangeWayCount(str); cout << "Possible ways to arrange: " << ans << endl; }
Output
Possible ways to arrange: 720