diff --git a/practical_exercises/key_exercises/函数模板.cpp b/practical_exercises/key_exercises/函数模板.cpp
index 1d3de68..b6263d6 100644
--- a/practical_exercises/key_exercises/函数模板.cpp
+++ b/practical_exercises/key_exercises/函数模板.cpp
@@ -1,19 +1,20 @@
-#include<iostream>
-#include<cstring>
+#include <cstring>
+#include <iostream>
 using namespace std;
 
-
-template<class T> T compareMax(T t1,T t2){
-    return t1>t2?t1:t2;
+template <class T>
+T compareMax(T t1, T t2) {
+  return t1 > t2 ? t1 : t2;
 }
 
-template<> char* compareMax<char *>(char *s1,char *s2){
-    return strcmp(s1,s2)>=0?s1:s2;
+template <>
+const char *compareMax<const char *>(const char *s1, const char *s2) {
+  cout << "[for debug]" << " call compareMax template" << endl;
+  return strcmp(s1, s2) >= 0 ? s1 : s2;
 }
-int main(int argc, char const *argv[])
-{
-    cout<<compareMax(1,2)<<endl;
-    cout<<compareMax("asda","qweq")<<endl;
-    system("pause");
-    return 0;
+int main(int argc, char const *argv[]) {
+  cout << compareMax(1, 2) << endl;
+  cout << compareMax("asda", "qweq") << endl;
+  system("pause");
+  return 0;
 }