链串实现建串、输入串（键盘输入）、输出串、插入串、删除串、取子串、串连接、串替换（指定位置替换）、求串长等运算。程序设计完整代码含函数设计思想，详细注释

好的，下面是链串的完整代码，包含各种基本操作的实现：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// 定义链式存储结构体
typedef struct node {
    char data;
    struct node *next;
} Node, *LinkStr;

// 初始化链串
void InitLinkStr(LinkStr *s) {
    *s = (LinkStr) malloc(sizeof(Node));
    (*s)->next = NULL;
}

// 从键盘输入字符串
void StrInput(LinkStr s) {
    char c;
    LinkStr p = s;
    while ((c = getchar()) != '\n') {
        LinkStr tmp = (LinkStr) malloc(sizeof(Node));
        tmp->data = c;
        tmp->next = NULL;
        p->next = tmp;
        p = p->next;
    }
}

// 输出链串
void StrOutput(LinkStr s) {
    LinkStr p = s->next;
    while (p != NULL) {
        printf("%c", p->data);
        p = p->next;
    }
    printf("\n");
}

// 插入链串
void StrInsert(LinkStr s, int pos, LinkStr t) {
    int i = 0;
    LinkStr p = s;
    while (p != NULL && i < pos - 1) {
        p = p->next;
        i++;
    }
    if (p == NULL || i > pos - 1) {
        printf("Insert failed!\n");
        return;
    }
    LinkStr q = t->next;
    while (q != NULL) {
        LinkStr tmp = (LinkStr) malloc(sizeof(Node));
        tmp->data = q->data;
        tmp->next = p->next;
        p->next = tmp;
        p = p->next;
        q = q->next;
    }
}

// 删除链串
void StrDelete(LinkStr s, int pos, int len) {
    int i = 0;
    LinkStr p = s;
    while (p != NULL && i < pos - 1) {
        p = p->next;
        i++;
    }
    if (p == NULL || i > pos - 1) {
        printf("Delete failed!\n");
        return;
    }
    LinkStr q = p->next;
    i = 0;
    while (q != NULL && i < len) {
        LinkStr tmp = q;
        q = q->next;
        free(tmp);
        i++;
    }
    p->next = q;
}

// 取子串
void SubStr(LinkStr s, int pos, int len, LinkStr *t) {
    int i = 0;
    LinkStr p = s->next;
    *t = (LinkStr) malloc(sizeof(Node));
    LinkStr q = *t;
    while (p != NULL && i < pos - 1) {
        p = p->next;
        i++;
    }
    if (p == NULL || i > pos - 1) {
        printf("SubStr failed!\n");
        return;
    }
    i = 0;
    while (p != NULL && i < len) {
        LinkStr tmp = (LinkStr) malloc(sizeof(Node));
        tmp->data = p->data;
        tmp->next = NULL;
        q->next = tmp;
        q = q->next;
        p = p->next;
        i++;
    }
}

// 串连接
void Concat(LinkStr s, LinkStr t, LinkStr *r) {
    LinkStr p = s->next;
    *r = (LinkStr) malloc(sizeof(Node));
    LinkStr q = *r;
    while (p != NULL) {
        LinkStr tmp = (LinkStr) malloc(sizeof(Node));
        tmp->data = p->data;
        tmp->next = NULL;
        q->next = tmp;
        q = q->next;
        p = p->next;
    }
    p = t->next;
    while (p != NULL) {
        LinkStr tmp = (LinkStr) malloc(sizeof(Node));
        tmp->data = p->data;
        tmp->next = NULL;
        q->next = tmp;
        q = q->next;
        p = p->next;
    }
}

// 串替换
void StrReplace(LinkStr s, int pos, int len, LinkStr t) {
    int i = 0;
    LinkStr p = s;
    while (p != NULL && i < pos - 1) {
        p = p->next;
        i++;
    }
    if (p == NULL || i > pos - 1) {
        printf("Replace failed!\n");
        return;
    }
    LinkStr q = t->next;
    i = 0;
    while (q != NULL) {
        LinkStr tmp = (LinkStr) malloc(sizeof(Node));
        tmp->data = q->data;
        tmp->next = p->next;
        p->next = tmp;
        p = p->next;
        q = q->next;
        i++;
    }
    StrDelete(s, pos+i, len);
}

// 求串长
int StrLength(LinkStr s) {
    int len = 0;
    LinkStr p = s->next;
    while (p != NULL) {
        len++;
        p = p->next;
    }
    return len;
}

int main() {
    LinkStr s, t, r;
    InitLinkStr(&s);
    InitLinkStr(&t);

    printf("Please input string s:\n");
    StrInput(s);

    printf("Please input string t:\n");
    StrInput(t);

    printf("String s is: ");
    StrOutput(s);

    printf("String t is: ");
    StrOutput(t);

    printf("After insert t into s from position 3:\n");
    StrInsert(s, 3, t);
    StrOutput(s);

    printf("After delete 3 characters from position 3:\n");
    StrDelete(s, 3, 3);
    StrOutput(s);

    printf("The sub string of s from position 2 with length 4 is:\n");
    SubStr(s, 2, 4, &r);
    StrOutput(r);

    printf("The concat string of s and t is:\n");
    Concat(s, t, &r);
    StrOutput(r);

    printf("After replace 3 characters from position 4 with t:\n");
    StrReplace(s, 4, 3, t);
    StrOutput(s);

    printf("The length of s is %d\n", StrLength(s));
    printf("The length of t is %d\n", StrLength(t));

    return 0;
}

以上代码实现了链串的初始化、输入、输出、插入、删除、子串、连接、替换、求长度等基本操作。