数据结构_字符串匹配

1.暴力匹配

int brute_one_match(const char *s, const char *t) {
    for (int j = 0; t[j]; j++)
    {
        if (s[j] == t[j]) continue;
        return 0;
    }
    return 1;
}

int brute_force(const char *s, const char *t) {
    for (int i = 0; s[i]; i++)
    {
        if (brute_one_match(s + i, t)) return i;
    }
    return -1;
}

2.hash匹配

int quick_mod(int a, int b, int c){
    int ans = 1, temp = a;
    while (b)
    {
        if (b & 1) ans = ans * temp % c;
        temp = temp * temp % c;
        b >>= 1;
    }
    return ans;    
}

int hash_match(const char *s, const char *t) {
    int len = strlen(t), base = 31, P = 9973, nbase = quick_mod(base, len, P);
    int h = 0, th = 0;
    for (int i = 0; t[i]; i++)
    {
        th = (th * base + t[i]) % P;
    }
    for (int i = 0; s[i]; i++)
    {
        h = (h * base + s[i]) % P;
        if (i >= len) h = (h - (s[i - len] * nbase % P) + P) % P;
        if (i + 1 < len) continue;
        if (h != th) continue;
        if (brute_one_match(s + i - len + 1, t)) return i - len + 1;
    }
    return -1;  
}

Q1: 哈希匹配算法算法时间复杂度？

O(n*m/p)

3.KMP算法

int *getNext(const char *t, int *n){
    *n = strlen(t);
    int *next = (int *)malloc(sizeof(int) * (*n));
    next[0] = -1;
    for (int i = 1, j = -1; t[i]; i++)
    {
        while (j != -1 && t[j + 1] != t[i])
        {
             j = next[j];
        }
        if (t[j + 1] == t[i]) j += 1;
        next[i] = j;
    }
    return next;
}

int kmp(const char *s, const char *t) {
    int len;
    int *next = getNext(t, &len);
    for (int i = 0, j = -1; s[i]; i++)
    {
        while (j != -1 && t[j + 1] != s[i])
        {
            j = next[j];
        }
        if (t[j + 1] == s[i]) j += 1;
        if (t[j + 1] == '\0') {
            free(next);
            return i - len + 1;
        }
    }
    free(next);
    return -1;
}

KMP优化：

int **getJump(int *next, const char *t, int n) {
    int **jump = (int **)malloc(sizeof(int *) * n);
    for (int i = 0; i < n; i++) jump[i] = (int *)malloc(sizeof(int) * 26);
    jump += 1;
    for (int i = 0; i < 26; i++) jump[-1][i] = -1;
    jump[-1][t[0] - 'a'] = 0;
    for (int i = 0, I = n - 1; i < I; i++)
    {
        for (int j = 0; j < 26; j++) jump[i][j] = jump[next[i]][j];
        jump[i][t[i+1] - 'a'] = i + 1;
    }
    return jump;
}

int kmp_opt(const char *s, const char *t) {
    int len;
    int *next = getNext(t, &len);
    int **jump = getJump(next, t, len);
    for (int i = 0, j = -1; s[i]; i++)
    {
        j = jump[j][s[i] - 'a'];
        if (j == len - 1) return i - len + 1;
    }
    free(next);
    for(int i = 0; i < len; i++) free(jump[i-1]);
    free(jump - 1);
    return -1;
}

4.Sunday算法

int sunday(const char *s, const char *t) {
    int tlen = strlen(t), slen = strlen(s);
    int jump[128] = {0};
    for (int i = 0; i < 128; i++) jump[i] = tlen + 1;
    for (int i = 0; t[i]; i++) jump[t[i]] = tlen - i;
    for (int i = 0; i + tlen <= slen; )
    {
        if (brute_one_match(s + i, t)) return i;
        i += jump[s[i + tlen]];
    }
    return -1;
}

5.shift-and算法

int shift_and(const char *s, const char *t) {
    int code[128] = {0}, n = 0;
    for (; t[n]; n++) code[t[n]] |= (1 << n);
    int p = 0;
    for (int i = 0; s[i]; i++)
    {
        p = (p << 1 | 1) & code[s[i]];
        if (p & (1 << (n - 1))) return i - n + 1;
    }
    return -1;    
}

all：

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

#define MAX_N 10000
#define DEFAULT_LEN 40
char s[MAX_N+5], t[MAX_N+5];

#define TEST(func) {    \
    char temp_s[MAX_N + 5]; \
    sprintf(temp_s, "%s(\"%s\", \"%s\") = %3d\n", #func, s, t, func(s, t)); \
    int n = DEFAULT_LEN - strlen(temp_s); \
    while (n--) printf(" "); \
    printf("%s", temp_s);    \
} 

int brute_one_match(const char *s, const char *t) {
    printf("brute_one_match called\n");
    for (int j = 0; t[j]; j++)
    {
        if (s[j] == t[j]) continue;
        return 0;
    }
    return 1;
}

int brute_force(const char *s, const char *t) {
    for (int i = 0; s[i]; i++)
    {
        if (brute_one_match(s + i, t)) return i;
    }
    return -1;
}

int quick_mod(int a, int b, int c){
    int ans = 1, temp = a;
    while (b)
    {
        if (b & 1) ans = ans * temp % c;
        temp = temp * temp % c;
        b >>= 1;
    }
    return ans;    
}

int hash_match(const char *s, const char *t) {
    int len = strlen(t), base = 31, P = 9973, nbase = quick_mod(base, len, P);
    int h = 0, th = 0;
    for (int i = 0; t[i]; i++)
    {
        th = (th * base + t[i]) % P;
    }
    for (int i = 0; s[i]; i++)
    {
        h = (h * base + s[i]) % P;
        if (i >= len) h = (h - (s[i - len] * nbase % P) + P) % P;
        if (i + 1 < len) continue;
        if (h != th) continue;
        if (brute_one_match(s + i - len + 1, t)) return i - len + 1;
    }
    return -1;  
}

int *getNext(const char *t, int *n){
    *n = strlen(t);
    int *next = (int *)malloc(sizeof(int) * (*n));
    next[0] = -1;
    for (int i = 1, j = -1; t[i]; i++)
    {
        while (j != -1 && t[j + 1] != t[i])
        {
             j = next[j];
        }
        if (t[j + 1] == t[i]) j += 1;
        next[i] = j;
    }
    return next;
}

int kmp(const char *s, const char *t) {
    int len;
    int *next = getNext(t, &len);
    for (int i = 0, j = -1; s[i]; i++)
    {
        while (j != -1 && t[j + 1] != s[i])
        {
            j = next[j];
        }
        if (t[j + 1] == s[i]) j += 1;
        if (t[j + 1] == '\0') {
            free(next);
            return i - len + 1;
        }
    }
    free(next);
    return -1;
}

int **getJump(int *next, const char *t, int n) {
    int **jump = (int **)malloc(sizeof(int *) * n);
    for (int i = 0; i < n; i++) jump[i] = (int *)malloc(sizeof(int) * 26);
    jump += 1;
    for (int i = 0; i < 26; i++) jump[-1][i] = -1;
    jump[-1][t[0] - 'a'] = 0;
    for (int i = 0, I = n - 1; i < I; i++)
    {
        for (int j = 0; j < 26; j++) jump[i][j] = jump[next[i]][j];
        jump[i][t[i+1] - 'a'] = i + 1;
    }
    return jump;
}

int kmp_opt(const char *s, const char *t) {
    int len;
    int *next = getNext(t, &len);
    int **jump = getJump(next, t, len);
    for (int i = 0, j = -1; s[i]; i++)
    {
        j = jump[j][s[i] - 'a'];
        if (j == len - 1) return i - len + 1;
    }
    free(next);
    for(int i = 0; i < len; i++) free(jump[i-1]);
    free(jump - 1);
    return -1;
}

int sunday(const char *s, const char *t) {
    int tlen = strlen(t), slen = strlen(s);
    int jump[128] = {0};
    for (int i = 0; i < 128; i++) jump[i] = tlen + 1;
    for (int i = 0; t[i]; i++) jump[t[i]] = tlen - i;
    for (int i = 0; i + tlen <= slen; )
    {
        if (brute_one_match(s + i, t)) return i;
        i += jump[s[i + tlen]];
    }
    return -1;
}

int shift_and(const char *s, const char *t) {
    int code[128] = {0}, n = 0;
    for (; t[n]; n++) code[t[n]] |= (1 << n);
    int p = 0;
    for (int i = 0; s[i]; i++)
    {
        p = (p << 1 | 1) & code[s[i]];
        if (p & (1 << (n - 1))) return i - n + 1;
    }
    return -1;    
}

int test_func(const char *s, const char *t) {
    return -1;
}

int main(int argc, char const *argv[])
{
    while (~scanf("%s%s", s, t))
    {
        //TEST(brute_force);
        //TEST(test_func);
        TEST(hash_match);
        TEST(kmp);
        TEST(kmp_opt);
        TEST(sunday);
    }
    
    return 0;
}