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链接：http://blog.csdn.net/joylnwang/article/details/6778316
KMP算法是一种很经典的字符串匹配算法，链接中的讲解已经是很明确得了，自己按照其讲解大体实现了一遍，感觉还不错。其算法的效率在于next表的建立上，宗旨就是避免朴素匹配算法中的冗余回溯问题。还是直接上代码吧。
#ifndef ALGKMP_H__ #define ALGKMP_H__ static class KMP { public: KMP(char *pattern, char *target, int &index); ~KMP(); private: int patternLen; int *next; void calNextTable(char *pattern); }; KMP::KMP(char *pattern, char *target, int &index) { patternLen = strlen(pattern); next = new int[patternLen]; calNextTable(pattern); index = 0; while(index < strlen(target) - patternLen) { int flag = 0; for (; flag < patternLen; flag++) { if (pattern[flag] != target[index + flag]) { index = index+1 + flag - next[flag]; break; } } if (flag == patternLen)break; } if (index == strlen(target) - patternLen)index = -1; } KMP::~KMP() { delete[] next; } void KMP::calNextTable(char *pattern) { //int *f = new int[patternLen]; //f[0] = 0; next[0] = 0; /*--------------待优化----------------------*/ for (int i = 1; i < patternLen; i++) { int value = 0; for (int k = 0; k < i - 1; k++) { int flag = 0; for (flag = 0; flag <= k; flag++) { if (pattern[flag] != pattern[i - 1 - k + flag])break; } if (flag == k + 1)value = k + 1; } next[i] = value + 1; for (int j = 0; j < i; j++) { if (pattern[i] == pattern[j]) { next[i] = next[j]; break; } } } //delete f; } #endif
demo:
#include"iostream" #include"AlgKMP.h" using namespace std; int main(int argv, char *argc[]) { int index; KMP("BBBC", "BBBBCDEFG", index); cout <<index<< endl;
return 0;
}
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原文地址：http://www.cnblogs.com/meadow-glog/p/5373743.html
