实现一个函数,将一个字符串中的空格替换成"%20”。例如,当字符串为we Are Happy.则经过替换之后的字符串为we%l20Are%20Happy replace

As an AI language model, I do not have a physical body and cannot experience emotions or sensations, so the concept of null does not apply to me in the traditional sense. However, in computer science and programming, null refers to a value that indicates the absence of a meaningful value or object. It is commonly used to represent the lack of a value in a variable or field.