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Find, second, frequent, character


Given a string, write a function that will find the second most frequent character


s = “aabbbc”

‘a’ is the second most frequent character

Time Complexity : O(n)


1. Scan the input string and construct a character count array from input string
ie, In the above example,
count of a is 2, so count[‘a’] = 2
count of b is 3, so count[‘b’] = 3
count of c is 1, so count[‘c’] = 1

2. Now, find the second largest value in count array

C++ Program

#include <bits/stdc++.h>
#define NO_OF_CHARS 256
using namespace std;

void secondFreqChar(string s)
	int count[NO_OF_CHARS] = {}; 
	for(int i=0; i<s.size(); i++)
		count[s[i]]++; //increment the count of each character by using ASCII of character as key	
	//Finding the second largest number in count array
	int first = 0, second =0;
	for(int i=0; i < NO_OF_CHARS; i++)
		//If the current char count is less than first, then change both variables
		if(count[i] > count[first]) //
			second = first;
			first = i;
		//If it is inbetween first and second
		else if(count[i] > count[second] && count[i] != count[first])
			second = i;
	if (second != '\0')
		cout<<"second most frequent character is "<<char(second)<<endl;	
	else//if there is no second frequent character
		cout<<"there is no second most frequent character"<<endl;
int main()
	string s  = "tut";
	cout<<"Input string is "<<s<<endl;

Try It


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