Data structure-4.4 strings, arrays and generalized tables

Preface-Data Structure

The data structure needs to be chewed repeatedly, and the answers to the problems encountered in the development can be obtained at any time.

Pattern matching

Exercise 1-BF pattern matching

• Set the target string s = "eddede" and the pattern string t = "cdc". The length of s is n (n 6), and the length of t is m (m=3). The pointer i is used to indicate the current comparison character position of the target string s, and the pointer j is used to indicate the current comparison character position of the pattern string t. The BF pattern matching process is shown below.
  

Exercise 2-KMP pattern matching

• Exercise 2: Set the target string s="aabaaab", the pattern string -*aaab". The length of s is n(n=9) and the length of t is m(m=5). Use a pointer to indicate the current comparison character position of the target string s , Use the pointer to indicate the current comparison character position of the pattern string t, the KMP pattern matching process is shown below.
  

Improvements to next nextvalue

to sum up

• Because next[j] = k
• pj = pk (that is, the characters are equal), so nextvalue[j] = nextvalue[k] = next[k] ,pj != pk, so nextvalue[j] = next[j],

example:

• 因为next[4] = 1, a4 = a1 = 0, next[1] = 0, nextval[4] = next[1] = 0;

• topic
  

• answer
  

• The time complexity of KMP is still O(n+m)