数据结构复习笔记（四）——串

串的基本数据类型

串的基本数据类型

定长顺序存储

初始化赋值

bool StrAssign(SString T, char *chars)
{
    int i;
    if (strlen(chars) > MAXSIZE)
    {
        for (i = 1; i <= MAXSIZE; ++i)
            T[i] = *(chars + i - 1);
        T[0] = MAXSIZE;
    }
    else
    {
        T[0] = strlen(chars); //p.s.此时T[0]存入的是int类型的数据,打印%s时无法显示
        for (i = 1; i <= T[0]; ++i)
            T[i] = *(chars + i - 1);
        return OK;
    }
}
//
int StrLength(SString s) {
    return s[0]+1;
}

bool StrCopy(SString T, SString s) {
    int slen = StrLength(s);
    if (!slen) {
        return ERROR;
    }
    for (int i = 1; i < slen; i++) {
        T[i] = s[i];
    }
    T[0] = slen;
    return OK;
}



void StrPrint(SString T) {
    
    int len = StrLength(T);
    for (int i = 1; i < len; i++) {
        cout << T[i]<<" ";
    }
    cout << endl;
}


bool StrCat(SString T, SString s) {
    int tLenght = StrLength(T);
    int sLength = StrLength(s);
    if (tLenght + sLength >= MAXSIZE) {
        return ERROR;
    }
    int j = 1;
    for (int i = tLenght; i < tLenght + sLength; i++) {
        
        T[i] = s[j];
        j++;
        if (j > sLength) {
            break;
        }
    }
    T[0] = tLenght + sLength;
    return OK;
}

堆分配存储

参考 https://blog.csdn.net/ta893115871/article/details/8119040

typedef struct {
    char *ch;
    int len;
} HString;

bool InitHString(HString* s) {
    s->ch = (char*)malloc(sizeof(char));
    if (NULL == s->ch)
        return ERROR;
    s->ch = NULL;
    s->len = 0;
    return OK;
}


bool StrAssign(HString *T, const char *s) {
    if (T->ch)
        free(T->ch);
    int length = 0, i;
    while (s[length] != '\0')
        length++;
    T->ch = (char*)malloc(length * sizeof(char));
    if (!T->ch)
        return ERROR;
    for (i = 0; i < length; i++)
        *(T->ch + i) = *(s + i);
    T->len = length;
    *(T->ch + T->len) = '\0';
    return OK;
}

朴素的模式匹配算法

int Index(SString T, SString S, int pos) {
    int i = pos;

    int j = 1;
    while (i <= S[0] && j <= T[0]) {
        if (S[i] == T[i]) {
            i++;
            j++;
        }
        else {
            i = i - j + 2; //退回到上次匹配的下一位
            j = 1;
        }
    }
    if (j > T[0]) {
        return i - T[0];
    }
    else
        return 0;
}

KMP模式匹配算法

参考 https://www.cnblogs.com/dusf/p/kmp.html
https://blog.csdn.net/x__1998/article/details/79951598

int KMP(char * t, char * p) 
{
    int i = 0; 
    int j = 0;
 
    while (i < strlen(t) && j < strlen(p))
    {
        if (j == -1 || t[i] == p[j]) 
        {
            i++;
                j++;
        }
        else 
                j = next[j];
        }
 
    if (j == strlen(p))
       return i - j;
    else 
       return -1;
}

void getNext(char * p, int * next)
{
    next[0] = -1;
    int i = 0, j = -1;
 
    while (i < strlen(p))
    {
        if (j == -1 || p[i] == p[j])
        {
            ++i;
            ++j;
            next[i] = j;
        }   
        else
            j = next[j];
    }
}