LintCode_204 Singleton

Singleton is a most widely used design pattern. If a class has and only has one instance at every moment, we call this design as singleton. For example, for class Mouse (not a animal mouse), we should design it in singleton.

You job is to implement a getInstance method for given class, return the same instance of this class every time you call this method.

Example

In Java:

A a = A.getInstance();A b = A.getInstance();

定义一个静态变量来解决：

class Solution {public:    /**     * @return: The same instance of this class every time     */    static Solution* instance;    static Solution* getInstance() {        if (instance == NULL) {            instance = new Solution();        }        return instance;    }};Solution* Solution::instance = NULL;