Find the character that repeats most in a string

Solution 1:

// declare an alphabet array
int counter[26] = {0};
char *string = "inputstringofcharacters"; 
char ch; int i=0;

// foreach alphabet in input string, increment counter by 1
while( ch = *(string + i++) ) {
    *(counter + (int)ch)++;    
}

// find the max of array.
int max_count = 0;
char max_element;

for( i=0; i<26 data-blogger-escaped-counter="" data-blogger-escaped-i="" data-blogger-escaped-if=""> max_count) {
        max_count = counter[i];
        max_element = (char)i;
    }
}

Complexity: 

Traverse complete array once, O(n) 

Traverse the count array once, O(26) 

Total complexity O(26*n) = O(n) 

Solution 2:

typedef struct node {
    char info;
    node *left, *right;
}NODE;

// traverse input and construct binary search tree O(n)

// find the max element in the binary search tree O(log n)

Complexity: O(n log n)