字符串的基本操作和模式匹配

#include <stdio.h>#include <stdlib.h>#define MAX_SIZE 100#define OK 1#define ERROR -1typedef int Status;

字符串的结构体

typedef struct{    char ch[MAX_SIZE];    int length;}String;

字符串长度初始化为0

Status StrInit(String *S){    S->length = 0;    return OK;}

生成一个值等于char的串

Status StrAssign(String *S, char chars[]){    int i;    for(i = 0; chars[i] != '\0'; i++)    {        S->ch[i] = chars[i];        S->length++;    }    return OK;}

输出字符串

void StrOutPut(String S){    int i;    for(i = 0; i < S.length; i++)    {        printf("%c", S.ch[i]);    }    printf("\n");}

创建一个字符串

void StrCreate(String *S){    char ch[MAX_SIZE];    int i;    S->length = 0;    printf("Please enter a string:\n");    scanf("%s",ch);    for(i = 0; ch[i] != '\0'; i++)    {        S->ch[i] = ch[i];        S->length++;    }}

比较两个字符串的大小
若返回正数，则S>S1
若返回负数，则S

Status StrCompare(String *S, String *S1){    int i;    for(i = 0; i < S->length && i < S1->length; i++)    {        if(S->ch[i] != S1->ch[i])        {            return S->ch[i] - S1->ch[i];        }    }    return S->length - S1->length;//若长度短的字符串已经比较完(例如：abcdefg和abcd)则长度长的字符串大  或  两字符串的相等(例如：ggjghsg和ggjghsg)}

连接两个字符串

Status Concat(String *S1, String *S2, String *S){    int i;    int j;    for(i = 0; i < S1->length; i++)    {        S->ch[i] = S1->ch[i];        S->length++;    }    for(j = 0; j < S2->length; j++)    {        S->ch[i] = S2->ch[j];        S->length++;        i++;    }    return OK;}

求字符串的长度

void StrLength(String *S){    printf("The length of the string is :%d\n", S->length);    printf("\n");}

求字符串的子串
pos是子串起始位置
len是子串长度

Status SubString(String S, int pos, int len){    int i;    if(pos < 0 || pos > S.length)//起始位置小于零或大于字符串的长度    {        printf("Irregular position.\n");    }    else if( pos + len > S.length)//字符串从pos开始到结束没有len位    {        printf("It's too long.\n");    }    else    {        for(i = pos - 1; i <= pos + len - 2; i++)        {            printf("%c", S.ch[i]);        }        printf("\n");    }    return OK;}

字符串的模式匹配

Status Index(String S, int pos, String T){    int i;    int j;    int tag =0;//标记位(遇到重复的字符时)    int posi = 0;//返回子串的起始位置    if(pos < 0 || pos >= S.length)    {        printf("Irregular position.\n");    }    else    {        i = pos - 1;        j = 0;        while(i < S.length && j < T.length)        {            if(S.ch[i] == T.ch[j])            {                if(j == 0)                {                    tag = i;                }                i++;                j++;            }            else            {                if(j != 0)                {                    i = tag + 1;                }                else                {                    i = i + 1;                }                posi = i;                j = 0;            }        }        if(j == T.length)        {            printf("success\n");            printf("position:%d\n", posi + 1);        }        else        {            printf("fail\n");        }    }    return OK;}

int main(){    int a = 0;    String S;    String S1;    String S2;    String S3;    char chars[MAX_SIZE];    char ch[MAX_SIZE];    char ch1[MAX_SIZE];    StrInit(&S);    printf("1.create a string equals char\n2.create a string\n3.compare S1 with S2\n4.connect two strings\n5.find a substring of length number\n6.string pattern matching\n");    printf("*****************\n");    printf("  S  :new string\n");    printf("S1,S2:S1 compare with S2\n");    printf("  S3 :S1+S2\n");    printf("*****************\n");    while(1)    {        printf("Please enter the operation code:");        scanf("%d", &a);        if(a == 1)        {            int res = 0;            printf("Please enter a string:\n");            scanf("%s", chars);            res = StrAssign(&S, chars);            if(res == 1)            {                printf("Copy success!\n");                StrOutPut(S);                StrLength(&S);            }            else            {                printf("Copy fail!\n");            }        }        else if(a == 2)        {            S.ch[0] = '\0';            S.length = 0;            StrCreate(&S);            StrOutPut(S);            StrLength(&S);        }        else if(a == 3)        {            int res = 0;            S1.ch[0] = '\0';            S1.length = 0;            S2.ch[0] = '\0';            S2.length = 0;            StrCreate(&S1);            StrCreate(&S2);            res = StrCompare(&S1, &S2);            if(res > 0)            {                printf("The first string is larger than the the second string.\n");            }            else if(res < 0)            {                printf("The first string is less than the second string.\n");            }            else if(res == 0)            {                printf("The first string is equal to the second string.\n");            }        }        else if(a == 4)        {            StrInit(&S3);            S1.ch[0] = '\0';            S1.length = 0;            S2.ch[0] = '\0';            S2.length = 0;            StrCreate(&S1);            StrCreate(&S2);            Concat(&S1, &S2, &S3);            printf("*************\n");            StrOutPut(S3);            StrLength(&S3);        }        else if(a == 5)        {            int g, h;            StrCreate(&S);            printf("Please enter position:");            scanf("%d", &g);            printf("Please enter length:");            scanf("%d", &h);            SubString(S, g, h);        }        else if(a == 6)        {            int b;            String T1;            String T2;            StrInit(&T1);            StrInit(&T2);            printf("Please enter a string:\n");            scanf("%s", ch);            StrAssign(&T1, ch);            printf("Please enter a string:\n");            scanf("%s", ch1);            StrAssign(&T2, ch1);            printf("Please enter a position:\n");            scanf("%d", &b);            Index(T1, b, T2);        }        else        {            printf("Operation coding error.\n");            printf("Please enter again.\n");        }    }`   return 0;}

运行结果：