How to find the two most common letters in a string? - c

Question

The purpose of my code is to tell the user what is the most common letter and the second most common letter in the string and replace them with each other, but my code doesn't work properly. It finds the most common letters but doesn't replace them or print them properly. What is the problem?
Example input:
i love this game i do do
Output (this line is printed):
Most common: i, 2nd most common: o
After that I expected this output, which is not printed:
o live thos game o di o di
Code:
int main()
{
char array[MAX_LEN] = {0};
int i = 0, j = 0;
int max = 0, secondMAX = 0, count = 0, save = 0;
char saveForNow = ' ', highest = ' ', secondHighest = ' ';
printf("Enter a string:\n");
fgets(array, MAX_LEN, stdin);
array[strcspn(array, "\n")] = 0;
for(i = 0; i < strlen(array); ++i)
{
for(j = 0; j < strlen(array); j++)
{
if(array[i] != ' ')
{
if(array[i] == array[j])
{
count++;
saveForNow = array[i];
}
}
}
if(count > max)
{
max = count;
highest = saveForNow;
}
else if((count < max) && (count > secondMAX))
{
secondMAX = count;
secondHighest = saveForNow;
}
count = 0;
}
//*I think the proplem is here
for(i = 0; i < strlen(array); i++)
{
if(array[i] == highest)
{
array[i] = secondHighest;
}
else if(array[i] == secondHighest);
{
array[i] = highest;
}
}
printf("Most common: %c, ", highest);
printf("2nd most common: %c\n", secondHighest);
printf("Swapped:\n");
printf("%s", array);
//*I think the proplem is here
}