Leetcode - 2231. Largest Number After Digit Swaps by Parity

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Input: num = 1234
Output: 3412
Explanation: Swap the digit 3 with the digit 1, this results in the number 3214.
Swap the digit 2 with the digit 4, this results in the number 3412.
Note that there may be other sequences of swaps but it can be shown that 3412 is the largest possible number.
Also note that we may not swap the digit 4 with the digit 1 since they are of different parities.

解決する

void swap(char arr[], int a, int b)
{
    char temp = arr[a];
    arr[a] = arr[b];
    arr[b] = temp;
}
/* '0' ~ '9' -> 48 ~ 57 */
bool compare(char a, char b)
{
    int ap = a % 2;
    int bp = b % 2;
    if (ap != bp)
        return false;
    if (a > b)
        return true;
    else
        return false;    
}
void greedy(char arr[], int size)
{
    for (int st_idx = 0; st_idx < size - 1; st_idx++) {
        for (int i = st_idx + 1; i < size; i++) {
            if (compare(arr[i], arr[st_idx]))
                swap(arr, i, st_idx);
        }
    }
}
int largestInteger(int num){
    int ret = 0, size = 0;
    char arr[11] = {0,};
    
    sprintf(arr, "%d", num);
    size = strlen(arr);
    greedy(arr, size);
    sscanf(arr, "%d", &ret);
    return ret;
}