数据结构——字符串的基本操作

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/************************author's email:wardseptember@gmail.comdata:2017.12.16************************/#include<iostream>#include <stdio.h>using namespace std;typedef struct {    char *ch;    int length;}Str;void initstr(Str *str);//初始化字符串int strassign(Str &str, char *ch);//赋值void printstring(Str str);//输出字符串int strlength(Str str);//求字符串长度int strcompare(Str s1, Str s2);//比较两个字符串int concat(Str &str, Str str1, Str str2);//连接两个字符串int substring(Str &subsstr, Str str, int pos, int len);//取主串的子串int clearstring(Str &str);//清空字符串int main() {    Str str,s1,s2,strcat,substr;    char ch1[50],ch2[50];    initstr(&str);    initstr(&s1);    initstr(&s2);    initstr(&strcat);    initstr(&substr);    strassign(str, "input string");    printstring(str);    cout << "字符串的长度为：" << strlength(str)<<endl;    cout << "请输入串1：";    gets_s(ch1);    cout << "请输入串2：";    gets_s(ch2);    strassign(s1, ch1);    strassign(s2, ch2);    //printstring(s1);    //printstring(s2);    cout << "两串比较，若结果大于0，则串1 ASCLL大于串2 ASCLL。结果为：";    cout<<strcompare(s1, s2)<<endl;    concat(strcat, s1, s2);    cout << "两串连接后为：";    printstring(strcat);    cout << "取得子串为：";    substring(substr, strcat, 3, 7);    printstring(substr);    cout << "清空所有字符串。"<<endl;    clearstring(str);    clearstring(s1);    clearstring(s2);    clearstring(strcat);    clearstring(substr);    cout << "所有字符串均被清空。" << endl;    return 0;}void initstr(Str *str) {    str->ch = NULL;    str->length = 0;}int strassign(Str &str, char *ch) {    if (str.ch)        free(str.ch);    int len = 0;    char *c = ch;    while (*c) {        ++len;        ++c;    }    if (len == 0) {        str.ch = NULL;        str.length = 0;        return 1;    }    else    {        str.ch = (char*)malloc(sizeof(char)*(len + 1));        if (str.ch == NULL)            return 0;        else {            c = ch;            for (int i = 0; i <= len; ++i) {                str.ch[i] = *c;                ++c;            }            str.length = len;            return 1;        }    }}void printstring(Str str) {    for (int i = 0; i < str.length; ++i)        cout << str.ch[i];    cout << endl;}int strlength(Str str) {    return str.length;}int strcompare(Str s1, Str s2) {    for (int i = 0; i < s1.length&&i < s2.length; ++i)        if (s1.ch[i] != s2.ch[i])            return s1.ch[i] - s2.ch[i];    return s1.length - s2.length;}int concat(Str &str, Str str1, Str str2) {    if (str.ch) {        free(str.ch);        str.ch = NULL;    }    str.ch = (char*)malloc(sizeof(char)*(str1.length + str2.length + 1));    if (str.ch == NULL)        return 0;    int i = 0;    while (i < str1.length) {        str.ch[i] = str1.ch[i];        i++;    }    int j = 0;    while (j <=str2.length) {        str.ch[i + j] = str2.ch[j];        ++j;    }    str.length = str1.length + str2.length;    return 1;}int substring(Str &substr, Str str, int pos, int len) {    if (pos < 0 || pos >= str.length || len < 0 || len > str.length - pos)        return 0;    if (substr.ch) {        free(substr.ch);        substr.ch = NULL;    }    if (len == 0) {        substr.ch = NULL;        substr.length = 0;        return 1;    }    else    {        substr.ch = (char*)malloc(sizeof(char)*(len + 1));        int i = pos;        int j = 0;        while (i < pos + len) {            substr.ch[j] = str.ch[i];            ++i;            ++j;        }        substr.ch[j] = '\0';        substr.length = len;        return 1;    }}int clearstring(Str &str) {    if (str.ch) {        free(str.ch);        str.ch = NULL;    }    str.length = 0;    return 1;}
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