字符变量

.gitignore

@@ -86,9 +86,10 @@ Module.symvers
 Mkfile.old
 dkms.conf
 
-# 自定义
+# 自定义过滤
 */output
 *.i
 *.s
 *.o
 *.swp
+.vscode

day4/d10.cpp

@@ -0,0 +1,15 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    char c = 'a'; // 1B
+    int m = 2;    // 4B
+    // 小字节转大字节, 会自动转换
+    m += c; // 先将c转换为int,再相加
+    cout << "m = " << m << endl;
+    // 大字节转小字节,会丢失精度,需要强制类型转换
+    cout << "m to char is " << (char)m << endl;
+    return 0;
+}

day4/d11.cpp

@@ -0,0 +1,11 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    cout << "'0' = " << (int)'0' << endl;
+    cout << 0 << endl;
+    cout << (int)'\0' << endl;
+    return 0;
+}

day4/d12.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+#include <regex> // 引入正则表达式库
+
+using namespace std;
+
+int main()
+{
+    string x;
+    cout << "输入一个字符:" << endl;
+    cin >> x;
+
+    regex regex_lower("[a-z]");
+    regex regex_upper("[A-Z]");
+    cout << regex_match(x, regex_lower) << regex_match(x, regex_upper) << endl;
+    // 正则表达式
+    if (regex_match(x, regex_lower)) // regex_match 匹配正则表达式
+    {
+        cout << (char)(x.at(0) - 32) << endl; // .at(0) 获取第一个字符
+    }
+    else if (regex_match(x, regex_upper))
+    {
+        cout << (char)(x.at(0) + 32) << endl;
+    }
+}

day4/d13.cpp

@@ -0,0 +1,24 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    // 字符串打印遇到\0则结束打印
+    string str1 = "abc\0good"; // abc\0good\0
+    cout << str1 << str1 << endl;
+    cout << "sizeof str1 = " << sizeof(str1) << endl; // 32B 32*8=256位
+
+    char str2[] = "disen666"; // 字符数组, 实际上也是一个字符串
+    cout << "str2 = " << str2 << endl;
+
+    char str3[] = {'d', 'i', 's', 'e', 'n'}; // 自动添加 '\0'
+    cout << "str3 = " << str3 << endl;
+    cout << "sizeof str3 = " << sizeof(str3) << endl; // 5B, 没算 '\0'
+
+    string str4 = "a";
+    cout << "sizeof str4 = " << sizeof(str4) << endl; // 32B 32*8=256位
+
+    return 0;
+}

day4/d8.cpp

@@ -0,0 +1,13 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    int x1, y1, x2, y2;
+    cout << "请输入两个点坐标, 格式如 x1 y1 x2 y2" << endl;
+    cin >> x1 >> y1 >> x2 >> y2;
+    cout << "P1(" << x1 << "," << y1 << ")"
+         << " P2(" << x2 << "," << y2 << ")" << endl;
+    return 0;
+}

day4/exercise_2.4.5.2.cpp

@@ -0,0 +1,12 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    int a, b;
+    cout << "输入两个数:" << endl;
+    cin >> a >> b;
+    cout << "最大值为: " << (a > b ? a : b) << endl;
+    return 0;
+}