#include "dna.h"
#include <stdio.h>
#include <vector>
#include <string>
#include <map>
#include <iostream>
#include <cmath>
#include <algorithm>
// g++ grader.cpp dna.cpp -o dna
using namespace std;
map<char, int> base;
struct pref {
int arr[3][3], copy[3][3];
pref() {
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
arr[i][j] = copy[i][j] = 0;
}
}
}
void add(pref p) {
for (int a = 0; a < 3; a++) {
for (int b = 0; b < 3; b++) {
arr[a][b] += p.arr[a][b];
}
}
}
void subt(pref p) {
for (int a = 0; a < 3; a++) {
for (int b = 0; b < 3; b++) {
arr[a][b] -= p.arr[a][b];
}
}
}
int dist() {
int d = 0;
for (int i = 0; i < 3; i++) {
int a = 0, b = 0;
for (int j = 0; j < 3; j++) {
copy[i][j] = arr[i][j];
a += arr[i][j];
b += arr[j][i];
}
if (a != b) return -1;
}
int unpaired = 0;
// directly swap a and b
for (int a = 0; a < 3; a++) {
for (int b = 0; b < a; b++) {
int v = min(arr[a][b], arr[b][a]);
copy[a][b] -= v;
copy[b][a] -= v;
d += v;
unpaired += copy[a][b] + copy[b][a];
}
}
unpaired /= 3;
unpaired *= 2;
return d + unpaired;
}
void output() {
cout << "==========\n";
for (int k = 0; k < 3; k++) {
for (int i = 0; i < 3; i++)
cout << arr[k][i] << " ";
cout << "\n";
}
cout << "==========\n";
}
};
vector<pref> prefix;
void init(string a, string b) {
int size = a.size() + 1;
prefix = vector<pref> (size);
base['A'] = 0;
base['C'] = 1;
base['T'] = 2;
prefix[0] = pref(); // A, C, T (1), A, C, T (2), diff
for (int k = 1; k < size; k++) {
int i = k-1;
prefix[k] = prefix[k-1];
int base_a = base[a[i]];
int base_b = base[b[i]];
prefix[k].arr[base_a][base_b]++;
// prefix[k].arr[base_b][base_a]++;
}
}
int get_distance(int x, int y) {
pref a = prefix[x], b = prefix[y+1];
b.subt(a);
// b.output();
return b.dist();
}
/*
*/
