leetcode 3008. 找出数组中的美丽下标 II

题目如下

数据范围

首先使用kmp算法统计两个串的出现下标，随后使用双指针匹配就行。这道题纯纯kmp模板题。

通过代码

class Solution {
public:
    vector<int> beautifulIndices(string s, string a, string b, int k) {
        int al = a.size();
        int bl = b.size();
        int n = s.size();
        vector<int> af;
        vector<int> bf;
        vector<int> ans;
        vector<int> an(al, 0), bn(bl, 0);
        for (int i = 1, j = 0; i < al; i++) {
            while (j > 0 && a[i] != a[j])
                j = an[j - 1];
            if (a[i] == a[j])
                j++;
            an[i] = j;
        }
        for (int i = 1, j = 0; i < bl; i++) {
            while (j > 0 && b[i] != b[j])
                j = bn[j - 1];
            if (b[i] == b[j])
                j++;
            bn[i] = j;
        }
        int j = 0;
        int i = 0;
        while (i < n) {
            if (s[i] == a[j]) {
                i++;
                j++;
            } else {
                if (j > 0) {
                    j = an[j - 1];
                } else {
                    i++;
                }
            }
            if (al == j) {
                //   cout << i<< endl;
                af.push_back(i - al);
                j = an[j - 1];
            }
        }
        i = j = 0;
        while (i < n) {
            if (s[i] == b[j]) {
                i++;
                j++;
            } else {
                if (j > 0) {
                    j = bn[j - 1];
                } else {
                    i++;
                }
            }
            if (bl == j) {
                bf.push_back(i - bl);
                j = bn[j - 1];
            }
        }
        int l = 0, r = 0;
        while (l < af.size() && r < bf.size()) {
            if (abs(af[l] - bf[r]) <= k) {
                ans.push_back(af[l]);
                l++;
            } else if (af[l] < bf[r]) {
                l++;
            } else {
                r++;
            }
        }
        return ans;
    }
};