How Calculate Time Complexity Of C Program?

#include<bits/stdc++.h>
using namespace std;
#define MAX_CHARS 160

// This function returns true if str1 and str2 are ismorphic
bool areIsomorphic(string str1, string str2)
{

  int m = str1.length(), n = str2.length();

  // Length of both strings must be same for one to one
  // corresponance
  if (m != n)
  return false;

  // To mark visited characters in str2
  bool marked[MAX_CHARS] = {false};

  // To store mapping of every character from str1 to
  // that of str2. Initialize all entries of map as -1.
  int map[MAX_CHARS];
  memset(map, -1, sizeof(map));

  // Process all characters one by on
  for (int i = 0; i < n; i++)
  {
    // If current character of str1 is seen first
    // time in it.
    if (map[str1[i]] == -1)
    {
      // If current character of str2 is already
      // seen, one to one mapping not possible
      if (marked[str2[i]] == true)
        return false;

      // Mark current character of str2 as visited
      marked[str2[i]] = true;

      // Store mapping of current characters
      map[str1[i]] = str2[i];
    }

    // If this is not first appearance of current
    // character in str1, then check if previous
    // appearance mapped to same character of str2
    else if (map[str1[i]] != str2[i])
      return false;
  }

  return true;
}

// Driver program
int main()
{
cout << areIsomorphic("bbb", "yyy") << endl;
cout << areIsomorphic("aab", "yyz") << endl;
return 0;
}