diff --git a/day11/d1.c b/day11/d1.c
new file mode 100644
index 0000000..4a593ef
--- /dev/null
+++ b/day11/d1.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int *create_int_arr(int n)
+{
+    // 申请内存空间
+    int *arr = (int *)malloc(n * sizeof(int));
+    // 条件判断时，常量放在前面，变量放在后面
+    if (NULL == arr)
+    {
+        // printf("malloc error\n");
+        perror("malloc error"); // 打印错误信息, perror 会打印出错误信息
+        return NULL;            // 返回空指针
+    }
+    perror("malloc success"); // 打印成功信息
+    return arr;               // 返回数组首地址
+}
+
+void input_int_data(int *q, int n)
+{
+    int temp = n;
+    // 输入数据
+    while (n--)
+    {
+        printf("请输入第%d个数据:", temp - n);
+        scanf("%d", q++);
+    }
+}
+
+void print_data(int *q, int n)
+{
+    // 打印数据
+    while (n--)
+        printf("%d ", *q++);
+    printf("\n");
+}
+
+int main()
+{
+    int *p = NULL; // NULL == 0,用来表示指针指向的内存空间不存在
+    p = create_int_arr(10);
+    input_int_data(p, 10);
+    print_data(p, 10);
+    free(p); // 释放内存空间
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d10.c b/day11/d10.c
new file mode 100644
index 0000000..ddfe4fb
--- /dev/null
+++ b/day11/d10.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main()
+{
+    char *p = (char *)malloc(32);
+    p = (char *)realloc(p, 48);
+    if (NULL == p)
+    {
+        perror("malloc");
+        return 1;
+    }
+    // strncpy 用于将特定长度的字符串拷贝到指定的内存空间中
+    strncpy(p, "disen,jack,lucy", 10); // 将 disen 的前 3 个字符拷贝到 p 中
+    printf("%s\n", p);
+    free(p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d11.c b/day11/d11.c
new file mode 100644
index 0000000..ecebdfc
--- /dev/null
+++ b/day11/d11.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void strcp(char *dest, char *src)
+{
+    int len = 0;
+    while (src[len++]) // 计算 src 的长度
+        ;
+
+    for (int i = 0; i < len - 1; i++) // len-1 会去掉字符串末尾的'\0'
+    {
+        *(dest + i) = *(src + i); // dest[i] = src[i];
+    }
+
+    // dest 原内容多余的部分要清空
+    while (dest[len - 1])
+    {
+        dest[len - 1] = 0;
+        len++;
+    }
+}
+
+int main()
+{
+    char p[100] = "disen,666,小马,888";
+    strcp(p, "disen,jack,lucy");
+    printf("%s\n", p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d12.c b/day11/d12.c
new file mode 100644
index 0000000..4a654d7
--- /dev/null
+++ b/day11/d12.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *str_cat(char *dest, char *src)
+{
+    int insert_pos = 0;
+    while (dest[insert_pos])
+        insert_pos++;
+
+    // 在 dest 的第一个 '\0' 处插入 src 内容
+    for (int i = 0; i <= strlen(src); i++)
+    // for (int i = 0; *(src + i); i++)
+    {
+        dest[insert_pos++] = *(src + i);
+    }
+
+    return dest;
+}
+
+int main()
+{
+    char p[100] = "good, 1\023";
+    str_cat(p, "小李子");
+    printf("%s\n", p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d12_2.c b/day11/d12_2.c
new file mode 100644
index 0000000..8e9f3df
--- /dev/null
+++ b/day11/d12_2.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// 拷贝 src 的前 n 个字符到 dest 中
+char *str_n_cat(char *dest, char *src, int n)
+{
+    int insert_pos = 0;
+    while (dest[insert_pos])
+        insert_pos++;
+
+    // 在 dest 的第一个 '\0' 处插入 src 内容
+    for (int i = 0; i < n; i++)
+    // for (int i = 0; *(src + i); i++)
+    {
+        dest[insert_pos++] = *(src + i);
+    }
+
+    return dest;
+}
+
+int main()
+{
+    char p[100] = "good, 1\023";
+    str_n_cat(p, "小李子", 6);
+    printf("%s\n", p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d13.c b/day11/d13.c
new file mode 100644
index 0000000..b3a96e5
--- /dev/null
+++ b/day11/d13.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// 比较两个字符串，如果 s1 > s2，返回 1；如果 s1 < s2，返回 -1；如果 s1 == s2，返回 0
+int cmp(const char *s1, const char *s2)
+{
+    while (*s1 && *s2)
+    {
+        if (*s1 > *s2) // 当前位置 *s1 > *s2
+            return 1;
+        else if (*s1 < *s2) // 当前位置 *s1 < *s2
+            return -1;
+        else // *s1 == *s2
+        {
+            s1++; // s1 指向下一个字符
+            s2++; // s2 指向下一个字符
+        }
+    }
+
+    if (*s1) // *s1 还有字符，*s2 没有字符
+        return 1;
+    if (*s2) // *s2 还有字符，*s1 没有字符
+        return -1;
+    return 0; // *s1 == *s2，返回相等
+}
+
+int main()
+{
+    char *p = "abc";
+    char *q = "abcd";
+    printf("%d\n", cmp(p, q));
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d13_2.c b/day11/d13_2.c
new file mode 100644
index 0000000..6a88325
--- /dev/null
+++ b/day11/d13_2.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// disen 版代码: 用于比较两个字符串，如果 s1 > s2，返回 1；如果 s1 < s2，返回 -1；如果 s1 == s2，返回 0
+int cmp(const char *s1, const char *s2)
+{
+    int i = 0;
+    while ((s1[i] || s2[i]) && s1[i] == s2[i])
+        i++;
+
+    int delta = s1[i] - s2[i];
+
+    if (delta == 0)
+        return 0;
+    else if (delta > 0)
+        return 1;
+    else
+        return -1;
+}
+
+int main()
+{
+    char *p = "abd";
+    char *q = "abcd";
+    printf("%d\n", cmp(p, q));
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d13_3.c b/day11/d13_3.c
new file mode 100644
index 0000000..7ae61ea
--- /dev/null
+++ b/day11/d13_3.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// 比较两个字符串，如果 s1 > s2，返回 1；如果 s1 < s2，返回 -1；如果 s1 == s2，返回 0
+int ncmp(const char *s1, const char *s2, int n)
+{
+    while (*s1 && *s2 && n--)
+    {
+        if (*s1 > *s2) // 当前位置 *s1 > *s2
+            return 1;
+        else if (*s1 < *s2) // 当前位置 *s1 < *s2
+            return -1;
+        else // *s1 == *s2
+        {
+            s1++; // s1 指向下一个字符
+            s2++; // s2 指向下一个字符
+        }
+    }
+    return 0; // *s1 == *s2，返回相等
+}
+
+int main()
+{
+    char *p = "abc";
+    char *q = "aacd";
+    printf("%d\n", ncmp(p, q, 3));
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d14.c b/day11/d14.c
new file mode 100644
index 0000000..3bed746
--- /dev/null
+++ b/day11/d14.c
@@ -0,0 +1,16 @@
+// strchr 和 strstr 的使用
+// strchr: 查找字符串中第一次出现某个字符的首地址位置
+// strrchr: 查找字符串中最后一次出现某个字符的首地址位置(反向查找)
+// strstr: 查找字符串中第一次出现某个字符串的首地址位置
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main()
+{
+    char *p = "disen";
+    strchr(p, 's'); // 查找字符串中第一次出现某个字符的首地址位置
+    printf("%ld\n", strchr(p, 's') - p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d15.c b/day11/d15.c
new file mode 100644
index 0000000..f26f93c
--- /dev/null
+++ b/day11/d15.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int valid_int(const char *s)
+{
+    int n = atoi(s);      // 转换成整型
+    int x = n / 100;      // 百位
+    int y = n % 100 / 10; // 十位
+    int z = n % 10;       // 个位
+    return (
+        x * x * x +
+            y * y * y +
+            z * z * z ==
+        n); // 水仙花数
+}
+
+int main(int argc, const char *argv[])
+{
+    printf("%d\n", valid_int(argv[1]));
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d16.c b/day11/d16.c
new file mode 100644
index 0000000..d12c7a0
--- /dev/null
+++ b/day11/d16.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, const char *argv[])
+{
+    char *p = "120";
+    printf("%ld\n", atol(p)); // atol: 转换成长整型
+
+    p = "12.3";
+    printf("%.2f\n", atof(p)); // atof: 转换成浮点数
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d17.c b/day11/d17.c
new file mode 100644
index 0000000..3c4c988
--- /dev/null
+++ b/day11/d17.c
@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main()
+{
+    char str[100] = "小明:21,,,.男.女,北京:haidian";
+    int i = 0;
+    char *delim = ":,."; // 以冒号、逗号、点号作为分隔符
+    char *ret[10];
+    ret[i] = strtok(str, delim); // 返回第一次切割的结果
+    while (ret[i] != NULL)
+    {
+        i++;
+        // 第二次及以后的切割要传入 NULL
+        ret[i] = strtok(NULL, delim);
+    }
+
+    char *title[10] = {"姓名", "年龄", "性别", "爱好", "地址", "区域"};
+    for (int j = 0; j < i; j++)
+    {
+        printf("%s: %s\n", title[j], ret[j]);
+    }
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d2.c b/day11/d2.c
new file mode 100644
index 0000000..513f064
--- /dev/null
+++ b/day11/d2.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+char *create_char_arr(int n)
+{
+    char *p = (char *)malloc(n * sizeof(char));
+    if (NULL == p)
+    {
+        perror("malloc error");
+        return NULL;
+    }
+    perror("malloc success");
+    return p;
+}
+
+void input_name(char **q)
+{
+    printf("输入数据: ");
+    scanf("%s", *q);
+}
+
+int main()
+{
+    char *p = NULL;
+    p = create_char_arr(20);
+    input_name(&p);
+    printf("输出数据: %s\n", p);
+    free(p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d3.c b/day11/d3.c
new file mode 100644
index 0000000..c699559
--- /dev/null
+++ b/day11/d3.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main()
+{
+    char *name = NULL;
+    name = (char *)malloc(32 * sizeof(char)); // 32个字节
+    if (NULL == name)
+        perror("malloc"); // 输出分配内存失败的原因
+    else
+        memset(name, 'a', 32); // 将 name 初始化为 32 个字节的 'a'
+    *(name + 30) = 'B';
+    *(name + 31) = '\0'; // 将 name 的最后一个字节设置为 '\0'
+    printf("%s\n", name);
+    free(name); // 释放内存空间
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d4.c b/day11/d4.c
new file mode 100644
index 0000000..36316a9
--- /dev/null
+++ b/day11/d4.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+int main()
+{
+    char *name = NULL;
+    name = (char *)calloc(4, 8 * sizeof(char)); // 说明: 4 * 8 = 32
+    if (NULL == name)
+        perror("calloc");
+    scanf("%s", name);
+    printf("%s\n", name);
+    free(name);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d5.c b/day11/d5.c
new file mode 100644
index 0000000..188f026
--- /dev/null
+++ b/day11/d5.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+int main()
+{
+    char(*names)[32] = (char(*)[32])calloc(3, 32 * sizeof(char)); // 说明: 4 * 32 = 128
+    for (int i = 0; i < 3; i++)
+    {
+        printf("第 %d 个人的名字: ", i + 1);
+        // names + i -> char(*)[32] 二维数组的首地址
+        // *(names + i) -> char[32] 一维数组的首地址 (*降维)
+        scanf("%s", *(names + i)); // *(names + i) == names[i]
+    }
+
+    for (int i = 0; i < 3; i++)
+        printf("%s\n", *(names + i)); // *(names + i) == names[i]
+
+    free(names);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d6.c b/day11/d6.c
new file mode 100644
index 0000000..cfd942d
--- /dev/null
+++ b/day11/d6.c
@@ -0,0 +1,114 @@
+// 设计列表数据结构操作函数，包含创建空列表，列表添加、删除和修改等操作
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+// 定义链表节点
+typedef struct node
+{
+    char name[32];
+    struct node *next;
+} Node;
+
+// 创建空链表
+Node *create_list()
+{
+    Node *head = (Node *)malloc(sizeof(Node));
+    if (NULL == head)
+    {
+        perror("malloc error");
+        return NULL;
+    }
+    memset(head, 0, sizeof(Node));
+    return head;
+}
+
+// 添加节点
+void add_node(Node *head, char *name)
+{
+    Node *p = head;
+    while (p->next != NULL)
+        p = p->next;
+    Node *new_node = (Node *)malloc(sizeof(Node));
+    if (NULL == new_node)
+    {
+        perror("malloc error");
+        return;
+    }
+    memset(new_node, 0, sizeof(Node));
+    strcpy(new_node->name, name);
+    p->next = new_node;
+}
+
+// 打印链表
+void print_list(Node *head)
+{
+    Node *p = head->next;
+    while (p != NULL)
+    {
+        printf("%s ", p->name);
+        p = p->next;
+    }
+    printf("\n");
+}
+
+// 删除节点
+void delete_node(Node *head, char *name)
+{
+    Node *p = head;
+    while (p->next != NULL)
+    {
+        if (strcmp(p->next->name, name) == 0)
+        {
+            Node *temp = p->next;
+            p->next = p->next->next;
+            free(temp);
+            return;
+        }
+        p = p->next;
+    }
+}
+
+// 修改节点
+void modify_node(Node *head, char *name, char *new_name)
+{
+    Node *p = head->next;
+    while (p != NULL)
+    {
+        if (strcmp(p->name, name) == 0)
+        {
+            strcpy(p->name, new_name);
+            return;
+        }
+        p = p->next;
+    }
+}
+
+// 释放链表
+void free_list(Node *head)
+{
+    Node *p = head;
+    while (p != NULL)
+    {
+        Node *temp = p;
+        p = p->next;
+        free(temp);
+    }
+}
+
+int main()
+{
+    Node *head = create_list();
+    add_node(head, "a");
+    add_node(head, "b");
+    add_node(head, "c");
+    add_node(head, "d");
+    print_list(head);
+    delete_node(head, "b");
+    print_list(head);
+    modify_node(head, "c", "e");
+    print_list(head);
+    free_list(head);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d6_2.c b/day11/d6_2.c
new file mode 100644
index 0000000..4c24aef
--- /dev/null
+++ b/day11/d6_2.c
@@ -0,0 +1,65 @@
+// 设计列表数据结构操作函数，包含创建空列表，列表添加、删除和修改等操作
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+int *create_list(int cap_size)
+{
+    int *p = (int *)malloc(cap_size * sizeof(int));
+    if (NULL == p)
+        perror("malloc error");
+    else
+        memset(p, 0, cap_size * sizeof(int));
+    return p;
+}
+
+int *add(int *p, int size, int element)
+{
+    // 判断当前的空间是否已满
+    int i = 0;
+    while (i < size && p[i] != 0) // *(p+i) = p[i]
+    {
+        i++;
+        // 这里不能用 p++, 因为会改变地址偏移量
+        // p++;
+    }
+
+    if (i < size) // 空间未满
+    {
+        p[i] = element; // 将 element 添加到空间中
+    }
+    else if (i == size)
+    {
+        printf("空间已满, 开始扩容\n");
+        int *new_p = (int *)realloc(p, (size + 1) * sizeof(int)); // 重新分配空间
+        if (NULL == p)
+            perror("realloc error");
+        else
+        {
+            p = new_p;
+            p[i] = element;
+        }
+        return p;
+    }
+}
+
+int main()
+{
+    int *p = create_list(4);
+    p[0] = 2, p[1] = 3, p[2] = 4;
+
+    for (int i = 0; i < 4; i++)
+        printf("%d ", *(p + i));
+    printf("\n");
+    add(p, 4, 100); // p[3] = 100;
+    add(p, 4, 200); // 100
+    add(p, 4, 300); // 100
+    add(p, 4, 400); // 100
+
+    for (int i = 0; i < 6; i++)
+        printf("%d ", *(p + i));
+    printf("\n");
+    free(p);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d6_3.c b/day11/d6_3.c
new file mode 100644
index 0000000..f5a35ab
--- /dev/null
+++ b/day11/d6_3.c
@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+int main()
+{
+    // 定义字符数组，接收用户输入的内容（最大值为 100 B）
+    char *p = (char *)malloc(100 * sizeof(char));
+
+    if (NULL == p)
+    {
+        perror("malloc");
+        return 1;
+    }
+    memset(p, 0, 100 * sizeof(char));
+    printf("data: ");
+    scanf("%s", p);
+
+    // strlen() 获取字符的个数
+    int len = 0;
+    while (p[len++])
+        ; // len = strlen(p);
+
+    if (len != 100)
+    {
+        printf("before realloc,%p\n", p);
+        // 重新分配空间
+        p = (char *)realloc(p, (len) * sizeof(char));
+        printf("after realloc,%p\n", p);
+    }
+
+    printf("%s, size of p: %d\n", p, len); // 重新分配空间后，p 的大小不变
+    free(p);                               // 释放空间
+
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d7.c b/day11/d7.c
new file mode 100644
index 0000000..850594f
--- /dev/null
+++ b/day11/d7.c
@@ -0,0 +1,27 @@
+// 内存泄漏
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+int *create(int n)
+{
+    int *p = (int *)malloc(n * sizeof(int)); // n*4
+    memset(p, 0, n * sizeof(int));
+    if (NULL == p)
+    {
+        perror("malloc error");
+    }
+    return p;
+}
+
+int main()
+{
+    int *p = create(5);
+    p[0] = 100;
+    printf("%d\n", *p); // *p = p[0]
+
+    // 用完之后，释放空间
+    free(p);
+
+    return 0; // p 指向的空间没有释放，内存泄漏
+}
\ No newline at end of file
diff --git a/day11/d7_2.c b/day11/d7_2.c
new file mode 100644
index 0000000..128198d
--- /dev/null
+++ b/day11/d7_2.c
@@ -0,0 +1,27 @@
+// 在 create 函数中申请的内存发生了泄漏
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> // memset
+
+void create(char *p, int n)
+{
+    p = (int *)malloc(n);
+    memset(p, '\0', n);
+    if (NULL == p)
+    {
+        perror("malloc error");
+    }
+}
+
+int main()
+{
+    int *p = NULL;
+    create(p, 32);
+    scanf("%s", p);
+    printf("==>%s\n", p);
+
+    // 用完之后，释放空间
+    free(p);
+
+    return 0; // p 指向的空间没有释放，内存泄漏
+}
\ No newline at end of file
diff --git a/day11/d7_3.c b/day11/d7_3.c
new file mode 100644
index 0000000..7333dc8
--- /dev/null
+++ b/day11/d7_3.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void create(char **p, int n) // **p = p[0]; *p = p[0]; p = &p[0]
+{
+    *p = (char *)malloc(n); // *p = p[0]
+    memset(*p, '\0', n);
+    if (NULL == *p)
+    {
+        perror("malloc error");
+    }
+}
+
+int main()
+{
+    char *p = NULL;
+    create(&p, 32);
+    scanf("%s", p);
+    printf("==>%s\n", p);
+    free(p);
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d8.c b/day11/d8.c
new file mode 100644
index 0000000..5ccb57d
--- /dev/null
+++ b/day11/d8.c
@@ -0,0 +1,29 @@
+// 自定义函数 str_len，计算字符串长度
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int str_len(const char *str)
+{
+    // const 作用: 防止str指针在函数内被修改
+    int len = 0;
+    while (str[len++])
+        ;
+    return len - 1; // 不需要 '\0'
+}
+
+int main()
+{
+    char content[100] = "";
+    while (1)
+    {
+        printf("data: ");
+        scanf("%s", content);
+        if (content[0] == 'q')
+            break; // 当输入 q 时，退出循环
+        // printf("%s len is %d\n", content, str_len(content));
+        // string.h 中的 strlen 函数
+        printf("%s len is %ld\n", content, strlen(content));
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/day11/d9.c b/day11/d9.c
new file mode 100644
index 0000000..1f0b49c
--- /dev/null
+++ b/day11/d9.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main()
+{
+    char *p = (char *)malloc(32);
+    if (NULL == p)
+    {
+        perror("malloc");
+        return 1;
+    }
+    // strcpy 用于字符串拷贝
+    strcpy(p, "disen");
+    printf("%s\n", p);
+    free(p);
+    return 0;
+}
\ No newline at end of file