URAL 1646 Godzilla Strikes Back!

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
typedef long long ll;
const int mod = 1000000000 + 7;
const int N = 100+10;
struct node {
    char s1
, s2
;
    int len1, len2, g;
};

char s
;
int len, f
;
node a
;

void init(node& x) {
    scanf("%s", x.s1);
    x.len1 = x.len2 = strlen(x.s1);
    for (int i = 0; i < x.len1; ++i)
        x.s2[i] = x.s1[x.len1 - i - 1];
    x.g = 0;
    int j = 0;
    for (int i = 0; i < x.len1; ++i) {
        while (j && x.s1[i] != s[j])
            j = f[j];
        if (x.s1[i] == s[j])
            ++ j;
        if (j == len) {
            ++ x.g;
            j = f[j];
        }
    }
    if (x.len1 >= len - 1)
        x.len1 = x.len2 = len - 1;
}
void make() {
    int j;
    f[0] = f[1] = 0;
    for (int i = 1; i < len; ++i) {
        j = f[i];
        while (j && s[j] != s[i])
            j = f[j];
        if (s[j] == s[i])
            f[i + 1] = j + 1;
        else
            f[i + 1] = 0;
    }
}
node get(node& x, node& y) {
    node re;
    re.g = (x.g + y.g) % mod;
    int j = 0;
    for (int i = x.len2 - 1; i >= 0; --i) {
        while (j && x.s2[i] != s[j])
            j = f[j];
        if (x.s2[i] == s[j])
            ++ j;
    }
    for (int i = 0; i < y.len1; ++i) {
        while (j && y.s1[i] != s[j])
            j = f[j];
        if (y.s1[i] == s[j])
            ++ j;
        if (j == len) {
            re.g = (re.g + 1) % mod;
            j = f[j];
        }
    }
    re.len1 = x.len1;
    for (int i = 0; i < x.len1; ++i)
        re.s1[i] = x.s1[i];
    if (re.len1 < len - 1) {
        for (int i = 0; i < y.len1; ++i) {
            re.s1[re.len1++] = y.s1[i];
            if (re.len1 == len - 1)
                break;
        }
    }
    //
    re.len2 = y.len2;
    for (int i = 0; i < y.len2; ++i)
        re.s2[i] = y.s2[i];
    if (re.len2 < len - 1) {
        for (int i = 0; i < x.len2; ++i) {
            re.s2[re.len2++] = x.s2[i];
            if (re.len2 == len - 1)
                break;
        }
    }
    return re;
}
int main() {
    int m, u, v, n;
    while (~scanf("%s", s)) {
        len = strlen(s);
        make();
        init(a[1]);
        init(a[2]);
        n = 2;
        scanf("%d", &m);
        while (m -- >0) {
            scanf("%d%d", &u, &v);
            a[++n] = get(a[u], a[v]);
        }
        printf("%d\n", a
.g);
    }
    return 0;
}