KMP算法复习

来源：互联网发布：手机淘宝上怎么退货编辑：程序博客网时间：2024/06/09 19:18

g++ (Ubuntu 4.9.2-10ubuntu13) 4.9.2下编译和运行通过

#include<iostream>#include<string.h>using namespace std;int * getnext(char* substr){    unsigned int i = 0;    int j = -1;    int n = strlen(substr);    int *next = new int(n);    next[0] = -1;    while (i < strlen(substr))    {        if (j == -1 || substr[i] == substr[j]) {            ++i;            ++j;            next[i] = j;        }        else {            j = next[j];        }    }    return next;}int KMP(char* str, char* substr){    int unsigned i = 0, j = 0;    int *next;    next = getnext(substr);    while (i < strlen(str) && j < strlen(substr))    {        if (str[i] == substr[j])        {            ++i;            ++j;        }        else        {            j = next[j];            if (j == -1)            {                j = 0;                ++i;            }        }    }    if (j == strlen(substr))        return (i - strlen(substr));    else        return 0;}int main(){    char* str = "abababc";    char* substr = "abc";    int i = KMP(str, substr);    cout << "This is the result:" << endl;    cout << i << endl;//result = 4    return 0;}

我在牛客网上implement str的解答：(不知道为什么通不过测试，请指教！)

class Solution {public:    int strStr(char *haystack, char *needle) {        int i = 0;        int j = 0;        int m = strlen(haystack);        int n = strlen(needle);        int *next = new int[n];        getnext(needle, next);        while (i < m && j < n)        {            if (j == -1 || haystack[i] == needle[j])            {                ++i;                ++j;            }            else            {                j = next[j];            }        }        if (j >= n)            return (i - j);        else            return -1;    }    void getnext(char *needle, int next[])    {        int i = 0, j = -1;        int n = strlen(needle);        next[0] = -1;        while (i <n) {            if (j == -1 || needle[i] == needle[j])            {                ++i;                ++j;                next[i] = j;            }             else                j = next[j];        }    }};

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