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#include <iostream>
#include <algorithm>
#include <array>
#include <climits>
#include <cassert>
#include "ai_str.h"
using namespace std;
static const int deltaxy[8][2] = {
{1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}, {-1, -1}, {0, -1}, {1, -1}
};
static const int deltaidx[8] = {
#define ITEM(_i) (BSZ * deltaxy[_i][1] + deltaxy[_i][0])
ITEM(0), ITEM(1), ITEM(2), ITEM(3), ITEM(4), ITEM(5), ITEM(6), ITEM(7)
#undef ITEM
};
static int findExtent(const Board &bd, int idx, int dir, uint8_t clr) {
const int dx = deltaxy[dir][0], dy = deltaxy[dir][1], didx = deltaidx[dir];
int x = idx % BSZ, y = idx / BSZ;
x += dx; y += dy; idx += didx;
for (int i = 0; i < RLEN - 1 && x > 0 && x < BSZ - 1 && y > 0 && y < BSZ - 1; i++) {
if (bd[idx] != 0 && bd[idx] != clr) return i;
x += dx; y += dy; idx += didx;
}
return RLEN - 1;
}
static int count(const Board &bd, int idx, int didx, uint8_t clr) {
int res = 0;
for (int i = 0; i < RLEN; i++) {
res += bd[idx] == clr;
idx += didx;
}
return res;
}
static int calcScore(const Board &bd, int idx, uint8_t myclr) {
array<array<int, NC>, 8> exts;
for (int dir = 0; dir < 8; dir++) {
for (int clr = 1; clr <= NC; clr++) {
exts[dir][clr - 1] = findExtent(bd, idx, dir, clr);
}
}
array<int, NC> score;
score.fill(0);
for (int dir = 0; dir < 4; dir++) {
const int dx = deltaxy[dir][0], dy = deltaxy[dir][1];
const int didx = deltaidx[dir];
assert(deltaxy[dir + 4][0] == -dx && deltaxy[dir + 4][1] == -dy);
for (int clr = 1; clr <= NC; clr++) {
int length = exts[dir][clr - 1] + exts[dir + 4][clr - 1] + 1;
if (length < RLEN) continue;
int start = idx + exts[dir][clr - 1] * didx;
int maxcnt = -1;
for (int i = 0; i < length - 4; i++) {
int cnt = count(bd, start, -didx, clr);
maxcnt = max(maxcnt, cnt);
start += -didx;
}
// Square the count to lay emphasis on larger lines
score[clr - 1] += maxcnt * maxcnt;
}
}
int tot = 0;
for (int i = 0; i < NC; i++) tot += score[i];
return -tot + 3 * score[myclr - 1];
}
int STR::calcMove(Board &bd, uint8_t myclr) {
assert(bd.bag.totalLeft() > 0);
int maxscore = INT_MIN, maxat = -1;
vector<int> moves = bd.getEdgeCells();
for (int idx : moves) {
int score = calcScore(bd, idx, myclr);
if (score > maxscore) {
maxscore = score;
maxat = idx;
}
}
return maxat;
}
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