func_code_string: #include <bits/stdc++.h>   using namespace std;   const int mod = 1000000007;   int n, fa[1200000], sf[1200000], len[1200000], f[1200000], g[1200000],       diff[1200000], c[1200000][30], p, np, cnt;   char s[1200000], a[1200000];   void upd(int &x, int y) { x = (x + y) % mod; }   int main() {     scanf( %s , s + 1);     n = strlen(s + 1);     for (int i = 1; i <= n / 2; ++i) {       a[i * 2 - 1] = s[i];       a[i * 2] = s[n - i + 1];     }     fa[0] = 1;     len[0] = 0;     fa[1] = 1;     len[1] = -1;     np = cnt = 1;     f[0] = 1;     for (int i = 1; i <= n; ++i) {       int w = a[i] -  a ;       for (p = np; a[i] != a[i - len[p] - 1]; p = fa[p])         ;       if (!c[p][w]) {         int q = fa[p], now = ++cnt;         len[now] = len[p] + 2;         for (; a[i] != a[i - len[q] - 1]; q = fa[q])           ;         fa[now] = c[q][w];         diff[now] = len[now] - len[fa[now]];         c[p][w] = np = now;         sf[now] = diff[now] == diff[fa[now]] ? sf[fa[now]] : fa[now];       } else         np = c[p][w];       for (int q = np; q; q = sf[q]) {         g[q] = f[i - len[sf[q]] - diff[q]];         if (diff[q] == diff[fa[q]]) upd(g[q], g[fa[q]]);         upd(f[i], g[q]);       }       if (i & 1) f[i] = 0;     }     printf( %d n , f[n]);     return 0;   }   