代码如下:

#include <iostream>
#include <string>
using namespace std;typedef struct
{char *ch;int length;
}String;bool initString(String &s)
{s.ch = nullptr;s.length = 0;return true;
}bool strAssign(String &s, const char *ch)
{int len = strlen(ch);s.ch = new char[len + 1];if (!s.ch) return false;for (int i = 0; i < len; i++){s.ch[i] = ch[i];}s.ch[len] = '\0';s.length = len;return true;
}bool strCopy(String &s, String t)
{if (!t.ch) return false;if (s.ch) delete[] s.ch;int len = strlen(t.ch);s.ch = new char[len + 1];for (int i = 0; i < len; i++){s.ch[i] = t.ch[i];}s.ch[len] = '\0';s.length = len;return true;
}bool strEmpty(String s)
{if (s.ch && s.length == 0) return true;return false;
}bool strCompare(String s, String ss)
{if (!s.ch) return false;if (!ss.ch) return false;for (int i = 0; i < s.length && i < ss.length; i++){if (s.ch[i] != ss.ch[i]){return s.ch[i] - ss.ch[i];}}return s.length - ss.length;
}int strLength(String s)
{return s.length;
}bool clearString(String &s)
{s.length = 0;return true;
}bool concatString(String &s, String s1, String s2)
{if (s.ch) delete[] s.ch;int len1 = s1.length;int len2 = s2.length;int len3 = len1 + len2;s.ch = new char[len3 + 1];for (int i = 0; i < len1; i++){s.ch[i] = s1.ch[i];}for (int i = len1; i < len3; i++){s.ch[i] = s2.ch[i];}s.ch[len3] = '\0';s.length = len3;return true;
}bool subString(String &sub, String s, int pos, int len)
{if (!s.ch) return false;if (pos <1 || pos > s.length || len < 0 || len > s.length - pos + 1) return false;if (sub.ch) delete[] sub.ch;if (!len){sub.ch = nullptr;sub.length = 0;}else{sub.ch = new char[len + 1];for (int i = 0; i < len; i++){sub.ch[i] = s.ch[pos - 1 + i];}sub.ch[len] = '\0';sub.length = len;}return true;
}int indexString(String s, String ss, int pos)
{if (pos > 0){int n = s.length;int m = ss.length;int i = pos;String sub;initString(sub);while (i <= n - m + 1){subString(sub, s, i, m);if (strCompare(sub, ss) != 0) ++i;else return i;}}return false;
}bool strInsert(String &s, int pos, String t)
{if (t.ch && s.ch){int len1 = t.length;int len2 = s.length;int len3 = len1 + len2;char *p = new char[len3 + 1];if (!p) return false;for (int i = 0; i < pos - 1 && i < len3; i++){p[i] = s.ch[i];}for (int i = 0; i < len1 && pos - 1 + i; i++){p[pos - 1 + i] = t.ch[i];}for (int i = 0; i < len3 - pos + 1 && pos + len1 - 1 + i < len3; i++)//pos + len1 - 1 + i < len3,防止数组越界，导致无法成功释放内存(数组越界以后，delete无法成功释放内存){p[pos + len1 - 1 + i] = s.ch[pos - 1 + i];}p[len3] = '\0';delete[] s.ch;s.ch = nullptr;s.ch = p;s.length = len3;return true;}return false;
}bool strDelete(String &s, int pos, int len)
{if (pos >= s.length) return false;if (pos + len >= s.length){s.length = len;s.ch[len] = '\0';}else{int start = pos + len - 1;while (start <= s.length){s.ch[pos - 1] = s.ch[start];++start;++pos;}s.length -= len;}return  true;
}bool replaceString(String &s, String t, String v)
{int len_s = s.length;int len_t = t.length;int len_v = v.length;int j = 1;String sub;initString(sub);while (len_s - j + 1 >= len_t){subString(sub, s, j, len_t);if (strCompare(sub, t) == 0){strDelete(s, j, len_t);strInsert(s, j, v);j += len_v;s.length = s.length + len_v - len_t;len_s = s.length;}else{j++;}}return true;
}bool destroyString(String &s)
{if (s.ch){delete[]s.ch;s.length = 0;}return true;
}int main()
{const char *ch = "dasfas";String s1;const char *ch1 = "dadas";String s2;const char *ch2 = "as";String s3;strAssign(s3, ch2);strAssign(s2, ch1);strAssign(s1, ch);strInsert(s1, 4, s2);strDelete(s1, 4, 5);cout << s1.ch << endl;cout << s2.ch << endl;replaceString(s1, s3, s2);cout << s1.ch << endl;String s4;initString(s4);strCopy(s4, s1);cout << s4.ch << endl;return 0;
}