#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
int N;
vector<array<int, 3>> A, B;
int c(char a)
{
return (a == 'A' ? 0 : (a == 'T' ? 1 : 2));
}
void init(std::string a, std::string b)
{
N = a.size();
A.resize(N, {0, 0, 0});
B.resize(N, {0, 0, 0});
if (a[0] != b[0])
{
A[0][c(a[0])]++;
B[0][c(b[0])]++;
}
for (int i = 1; i < N; i++)
{
A[i][0] = A[i - 1][0];
A[i][1] = A[i - 1][1];
A[i][2] = A[i - 1][2];
B[i][0] = B[i - 1][0];
B[i][1] = B[i - 1][1];
B[i][2] = B[i - 1][2];
if (a[i] != b[i])
{
A[i][c(a[i])]++;
B[i][c(b[i])]++;
}
}
}
int get_distance(int x, int y)
{
array<int, 3> dA = A[y], dB = B[y];
if (x != 0)
{
dA[0] -= A[x - 1][0];
dA[1] -= A[x - 1][1];
dA[2] -= A[x - 1][2];
dB[0] -= B[x - 1][0];
dB[1] -= B[x - 1][1];
dB[2] -= B[x - 1][2];
}
if (dA == dB)
{
return (1 + dA[0] + dA[1] + dA[2]) / 2;
}
return -1;
}
