Daily LeetCode – day0107 0791. Custom Sort String

// 0791. Custom Sort String
class Solution {
    public String customSortString(String order, String s) {
        int[] lettersQuantity = new int[123];
        for (char letter : s.toCharArray()) {
            ++lettersQuantity[letter];
        }
        StringBuilder sb = new StringBuilder();
        for (char letter : order.toCharArray()) {
            int quantity = lettersQuantity[letter];
            lettersQuantity[letter] = 0;
            for (int i = 0; i < quantity; ++i) {
                sb.append(letter);
            }
        }
        for (char c = 'a'; c <= 'z'; ++c) {
            int quantity = lettersQuantity[c];
            for (int i = 0; i < quantity; ++i) {
                sb.append(c);
            }
        }
        return sb.toString();
    }
}

学习笔记：
这是一道简单的字符串题。
说是字符串，其实考验的是排序和贪心的算法。