116 lines
2.9 KiB
C++
116 lines
2.9 KiB
C++
/**
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* @file -
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* @author jingqi
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* @date 2012-10-18
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* @last-edit 2012-11-13 21:36:50 jingqi
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* @ref https://blog.csdn.net/jingqi_se/article/details/14055709
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*/
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#ifndef ___HEADFILE_A04A7FB7_1516_4EF0_A8B9_44C5AABBF7EC_
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#define ___HEADFILE_A04A7FB7_1516_4EF0_A8B9_44C5AABBF7EC_
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#include <assert.h>
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#include <string>
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namespace nut
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{
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/**
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* 构建KMP自动状态机(特征码)
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*
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* @param target 长度为 len 的字符串，即要搜索的字符串子串
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* @param next 长度为 len 的缓冲区，用于存放生成的KMP自动状态机(特征码)
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*/
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inline void kmp_build_next(const char *target, int *next, size_t len)
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{
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assert(NULL != target && NULL != next && len > 0);
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if (len > 0)
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next[0] = 0;
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size_t i = 1;
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int state = 0;
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while (i < len)
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{
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if (target[i] == target[state])
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next[i++] = ++state;
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else if (0 == state)
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next[i++] = 0;
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else
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state = next[state - 1];
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}
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}
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/**
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* 更新KMP状态
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*
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* @param c 输入的单个字符
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* @param state 当前状态
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* @param target 要搜索的字符串子串
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* @param next KMP特征码
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* @return 新的状态
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*/
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inline int kmp_update(char c, int state, const char *target, const int *next)
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{
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assert(state >= 0 && NULL != target && NULL != next);
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while (true)
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{
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if (c == target[state])
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return ++state;
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else if (0 == state)
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return 0;
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else
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state = next[state - 1];
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}
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}
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/**
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* KMP字符串搜索
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*
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* @param src 被搜索的字符串
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* @param start 开始搜索的位置
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* @param target 要搜索的字符串子串
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* @param next KMP特征码(长度与target相同)
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*/
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inline int kmp_search(const char *src, size_t len_src, size_t start, const char *target, const int *next, size_t len_target)
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{
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assert(NULL != src && NULL != target && NULL != next);
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size_t i = start;
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int state = 0; // 状态，其实代表着已经匹配的字符串长度
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while (i < len_src && ((size_t) state) < len_target)
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state = kmp_update(src[i++], state, target, next);
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if (state == (int)len_target)
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return i - len_target;
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return -1;
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}
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/**
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* KMP字符串搜索
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*
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* 这里对于要搜索字符串的KMP特征码只做局部缓存，如果有特殊需求，例如被搜索的字符串不连续的存放在不同位置，
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* 则可使用其他函数组合使用(参见本函数的实现)
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*
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* @param src 被搜索的字符串
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* @param start 搜索开始的位置
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* @param target 要搜索的字符串子串
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*/
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inline int kmp_search(const std::string& src, size_t start, const std::string& target)
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{
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int *next = new int[target.length()];
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kmp_build_next(target.c_str(), next, target.length());
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const int ret = kmp_search(src.c_str(), src.length(), start, target.c_str(), next, target.length());
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delete[] next;
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return ret;
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}
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inline int kmp_search(const char *src, size_t len_src, const char *target, size_t len_target)
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{
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int *next = new int[len_target];
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kmp_build_next(target, next, len_target);
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const int ret = kmp_search(src, len_src, 0, target, next, len_target);
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delete[] next;
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return ret;
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}
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}
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#endif
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