解释代码 void getNext(string p, vector<int>& next) { int j = 0, k = -1; next[0] = -1; while (j < p.size() - 1) { if (k == -1 || p[j] == p[k]) { ++j; ++k; if (p[j] != p[k]) next[j] = k; else next[j] = next[k]; } else k = next[k]; } } int kmp(string s, string p) { vector<int> next(p.size()); getNext(p, next); int i = 0, j = 0; while (i < s.size() && j < p.size()) { if (j == -1 || s[i] == p[j]) { ++i; ++j; } else j = next[j]; } if (j == p.size()) return i - j; else return -1; }

Explanation of the code:

The given code is a function named "getNext", which takes a string "p" and a vector "next" as input parameters. The function doesn't have a return value (void).

This function generates the "next" array for the KMP algorithm, which is used for pattern matching in strings. The "next" array is used to find the proper prefix-suffix match in the pattern to avoid redundant comparisons in the text.

The function initializes two pointers "i" and "j" to 0 and assigns the value of 0 to the first element of the "next" vector. The for loop iterates through each character of the pattern string "p" and generates the "next" values for each character.

The while loop checks for the conditions (i>0 && p[i]!=p[j]), if true, then it resets the value of "j" to the element at position "j-1" in the "next" vector. This is because we are trying to find the longest possible suffix of "p" that is also a proper prefix. If we find a partial match, we keep reducing the length of the possible matches until we find the longest one possible.

After that, the while loop checks another condition (p[i]==p[j]), if true, then it increments the values of "i" and "j" and assigns the value of "j" to the element at position "i" in the "next" vector. This is because we have found a proper prefix-suffix match of length "i+1", and we store this value in the "next" vector for further matching operations.

Finally, the function returns the "next" vector. The "next" array generated by this function is used in the KMP algorithm to match the pattern string in any text string.