HDU 3683

因为少了一句if，这个AC迟来了一年...
解法：假设A先手，B后手。
    1.如果A有必胜点，放下去即连成5个，那么A一步获胜。
    2.如果B有两个以上的必胜点，那么B两步必胜。
    3.如果B只有一个必胜点，那么A第一步肯定放在B的必胜点上。再判断A是否有两个以上的必胜点，如果有，A三步获胜。
    4.枚举A第一步的走法，如果能走出两个以上的必胜点，那么A三步获胜。
    5.如果以上情况都不成立，那三步之内没人可以获胜。

#include <iostream>
using namespace std;

struct POINT
{
    int x, y;
};

int n, white, black;
int player, other;
int map[15][15];
int dir[4][2] = {{0, 1}, {1, 0}, {1, 1}, {1, -1}};
char str[][10] = {"", "white", "black"};

bool ReadCase()
{
    int i, col;
    POINT tmp;

    scanf("%d", &n);
    if (n == 0)
    {
        return false;
    }

    memset(map, 0, sizeof(map));
    white = black = 0;
    for (i = 0; i < n; i++)
    {
        scanf("%d %d %d", &tmp.x, &tmp.y, &col);
        if (col == 0)
        {
            white++;
            map[tmp.x][tmp.y] = 1;
        }
        else
        {
            black++;
            map[tmp.x][tmp.y] = 2;
        }
    }
    return true;
}

bool Check()
{
    if (black == white)
    {
        player = 2;
        other = 1;
    }
    else if (black == white + 1)
    {
        player = 1;
        other = 2;
    }
    else
    {
        return false;
    }
    return true;
}

bool Bound(POINT p)
{
    return p.x >= 0 && p.x <= 14 && p.y >= 0 && p.y <= 14;
}

int GetMaxLength(POINT p, int c)
{
    int res = 0;
    for (int i = 0; i < 4; i++)
    {
        int len = 0;
        POINT tmp = p;
        while (true)
        {
            tmp.x = tmp.x + dir[i][0];
            tmp.y = tmp.y + dir[i][1];
            if (!Bound(tmp) || map[tmp.x][tmp.y] != c)
            {
                break;
            }
            len++;
        }
        tmp = p;
        while (true)
        {
            tmp.x = tmp.x - dir[i][0];
            tmp.y = tmp.y - dir[i][1];
            if (!Bound(tmp) || map[tmp.x][tmp.y] != c)
            {
                break;
            }
            len++;
        }
        len++;
        if (len > res)
        {
            res = len;
        }
    }
    return res;
}

int GetWinPoint(POINT &p, int c)
{
    int num = 0;
    for (int i = 0; i < 15; i++)
    {
        for (int j = 0; j < 15; j++)
        {
            POINT tmp;
            tmp.x = i;
            tmp.y = j;
            int a = 0;
            if (map[tmp.x][tmp.y] == 0 && (a = GetMaxLength(tmp, c)) >= 5)
            {
                num++;
                if (num == 1)
                {
                    p = tmp;
                }
            }
            //cout << a << endl;
        }
    }
    return num;
}

void Solve()
{
    if (!Check())
    {
        printf("Invalid.\n");
        return;
    }
    POINT p, p2;
    int num;
    if (GetWinPoint(p, player) >= 1)
    {
        printf("Place %s at (%d,%d) to win in 1 move.\n", str[player], p.x, p.y);
        return;
    }
    if ((num = GetWinPoint(p, other)) >= 2)
    {
        printf("Lose in 2 moves.\n");
        return;
    }
    if (num == 1)
    {
        map[p.x][p.y] = player;
        if (GetWinPoint(p2, player) >= 2)
        {
            printf("Place %s at (%d,%d) to win in 3 moves.\n", str[player], p.x, p.y);
            return;
        }
    }
    else
    {
        for (int i = 0; i < 15; i++)
        {
            for (int j = 0; j < 15; j++)
            {
                if (map[i][j] == 0)
                {
                    map[i][j] = player;
                    if (GetWinPoint(p2, player) >= 2)
                    {
                        printf("Place %s at (%d,%d) to win in 3 moves.\n", str[player], i, j);
                        return;
                    }
                    map[i][j] = 0;
                }
            }
        }
    }
    printf("Cannot win in 3 moves.\n");
}

int main()
{
    while (ReadCase())
    {
        Solve();
    }
    return 0;
}