最佳答案
如何向字符串添加“0”填充,使字符串长度始终为4?
例子
If input "1", 3 padding is added = 0001
If input "25", 2 padding is added = 0025
If input "301", 1 padding is added = 0301
If input "4501", 0 padding is added = 4501