KMP算法二

KMP算法二：

#include <string>
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;

class Solution
{
public:
    void GetNext(string subStr, vector<int> &next) {
        int i = 0;
        int j = -1;
        next[0] = -1;
        int lengthOfSubStr = subStr.size();
        while (i < lengthOfSubStr - 1) {
            if ((j == -1) || subStr[i] == subStr[j]) {
                i++;
                j++;
                next[i] = j;
            } else {
                j = next[j];
            }
        }
        return;
    }
    void PrintNext(const vector<int> &next) {
        for (const auto &val : next) {
            cout << val << ' ';
        }
        cout << endl;
    }
    int Kmp(string mainStr, string subStr) {
        int lengthOfMainStr = mainStr.size();
        int lenghtOfSubStr = subStr.size();
        if ((lengthOfMainStr == 0) || (lenghtOfSubStr == 0) || lengthOfMainStr < lenghtOfSubStr) {
            return -1;
        }
        vector<int> next(lenghtOfSubStr);
        GetNext(subStr, next);
        int i = 0;
        int j = 0;
        while ((i < lengthOfMainStr) && (j < lenghtOfSubStr)) {
            if ((j == -1) || mainStr[i] == subStr[j]) {
                i++;
                j++;
            } else {
                j = next[j];
            }
        }
        if (j == lenghtOfSubStr) {
            return i - j;
        }
        return -1;
    }
};

int main()
{
    Solution *test = new Solution();
    string text = "ABABABCABAABABABABA";
    string pattern = "ABABCABAA";
    vector<int> next(pattern.size());
    test->GetNext(pattern, next);
    test->PrintNext(next); // -1, 0, 0, 1, 2, 0, 1, 2, 3
    cout << test->Kmp(text, pattern) << endl; // 2
    system("pause");
    return 0;
}

运行效果：