update

design_pattern/singleton/iazysingleton.cpp

@@ -0,0 +1,19 @@
+//
+// Created by light on 20-2-6.
+//
+
+class singleton {
+private:
+    singleton() {}
+    static singleton *p;
+public:
+    static singleton *instance();
+};
+
+singleton *singleton::p = nullptr;
+
+singleton* singleton::instance() {
+    if (p == nullptr)
+        p = new singleton();
+    return p;
+}