题目链接：https://www.luogu.com.cn/problem/P4173
解题思路：完全来自 Ebola大佬的博客
（理解了思路，自己手推了一下）
最后的式子用 FFT 求卷积。
示例程序：
#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 5;
using cd = complex<double>;
const double PI = acos(-1);void fft(vector<cd>&a, int type) {int n = a.size();if (n == 1) return;vector<cd> a0(n/2), a1(n/2);for (int i = 0; i < n/2; i++) {a0[i] = a[i * 2];a1[i] = a[i * 2 + 1];}fft(a0, type);fft(a1, type);cd wn(cos(2 * PI / n), type * sin(2 * PI / n));cd w(1, 0);for (int k = 0; k < n/2; k++) {cd t = w * a1[k];a[k] = a0[k] + t;a[k + n/2] = a0[k] - t;w *= wn;}
}int m, n, a[maxn], b[maxn], limit = 1;
char s[maxn], t[maxn];int query(int a[], int l, int r) {int res = a[r];if (l) res -= a[l-1];return res;
}vector<int> res;
double ans[maxn];bool check(int x) {long long res = 0;for (int i = 0; i < m; i++)res += a[i] * a[i] * a[i] * b[i+x]+ a[i] * b[i+x] * b[i+x] * b[i+x]- 2 * a[i] * a[i] * b[i+x] * b[i+x];return res == 0;
}int main() {scanf("%d%d%s%s", &m, &n, s, t);for (int i = 0; i < m; i++) {if (s[i] == '*')a[i] = 0;elsea[i] = s[i] - '0' + 1;}for (int i = 0; i < n; i++) {if (t[i] == '*')b[i] = 0;elseb[i] = t[i] - '0' + 1;}while (limit < n + m + 1)limit <<= 1;vector<cd> f(limit), g(limit);for (int i = 0; i < m; i++)f[i] = a[i] * a[i] * a[i];for (int i = 0; i < n; i++)g[n - i] = b[i];fft(f, 1);fft(g, 1);for (int i = 0; i < limit; i++)f[i] *= g[i];fft(f, -1);for (int i = 0; i+m-1 < n; i++)ans[i] += f[n-i].real() / limit;fill(f.begin(), f.end(), 0);fill(g.begin(), g.end(), 0);for (int i = 0; i < m; i++)f[i] = a[i];for (int i = 0; i < n; i++)g[n - i] = b[i] * b[i] * b[i];fft(f, 1);fft(g, 1);for (int i = 0; i < limit; i++)f[i] *= g[i];fft(f, -1);for (int i = 0; i+m-1 < n; i++)ans[i] += f[n-i].real() / limit;fill(f.begin(), f.end(), 0);fill(g.begin(), g.end(), 0);for (int i = 0; i < m; i++)f[i] = a[i] * a[i];for (int i = 0; i < n; i++)g[n - i] = b[i] * b[i];fft(f, 1);fft(g, 1);for (int i = 0; i < limit; i++)f[i] *= g[i];fft(f, -1);for (int i = 0; i+m-1 < n; i++)ans[i] -= 2 * f[n-i].real() / limit;for (int i = 0; i+m-1 < n; i++) {if (abs(ans[i]) < 0.5) {res.push_back(i+1);}}int k = res.size();printf("%d\n", k);for (auto x : res)printf("%d ", x);return 0;
}