There are n identical dice, each with k faces labeled 1 to k. Roll the number of dice so that the sum of the numbers facing up equals the target; Count the occurrence frequency of the smallest letter in the string s (in Lexicographic order order), where s is a non empty string; In an integer array, returns the maximum sum of elements that can be obtained from a non empty subarray (continuous elements) after performing an optional delete operation; An array of integers where each element is different, find all pairs of elements with the smallest absolute difference.