187.cpp

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

// CPP function to find the
// second most frequent character
// in a given string 'str'
char getSecondMostFreq(string str)
{
	// count number of occurrences of every character.
	int count[NO_OF_CHARS] = {0}, i;
	for (i = 0; str[i]; i++)
		(count[str[i]])++;

	// Traverse through the count[] and
	// find second highest element.
	int first = 0, second = 0;
	for (i = 0; i < NO_OF_CHARS; i++)
	{
		/* If current element is smaller
		than first then update both
		first and second */
		if (count[i] > count[first])
		{
			second = first;
			first = i;
		}

		/* If count[i] is in between first
		and second then update second */
		else if (count[i] > count[second] &&
				count[i] != count[first])
			second = i;
	}

	return second;
}

// Driver code
int main()
{
	string str = "geeksforgeeks";
	char res = getSecondMostFreq(str);
	if (res != '\0')
		cout << "Second most frequent char is " << res;
	else
		cout << "No second most frequent character";
	return 0;
}