极小极大搜索 的个人理解（alpha-beta剪枝）

主要算法依据就是根据极大极小搜索实现的。

苦逼的是，查了两个晚上的错，原来最终是判断函数写错了。。瞬间吐血！

ps. 据说加一句 if sum < 4 printf("#####\n")会变态的快，不过懒得加了

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <cmath>
#include <utility>
#include <vector>
#include <queue>
#include <set>
#define INF 0x3f3f3f3f

using namespace std;

int map[4][4], sum, winx, winy;
char c;

bool check(int otherplayer)
{
    for(int i = 0; i < 4; i ++)
    {
        int tmp = 0;
        for(int j = 0; j < 4; j ++)
            tmp += (map[i][j] == otherplayer);
        if(tmp == 4)
            return 1;
    }
    for(int j = 0; j < 4; j ++)
    {
        int tmp = 0;
        for(int i = 0; i < 4; i ++)
            tmp += (map[i][j] == otherplayer);
        if(tmp == 4)
            return 1;
    }
    int tmp1 = 0, tmp2 = 0;
    for(int i = 0; i < 4; i ++)
    {
        tmp1 += (map[i][i] == otherplayer);
        tmp2 += (map[3-i][i] == otherplayer);
    }
    if(tmp1 == 4 || tmp2 == 4)
        return 1;
    return 0;
}

int alpha_beta(int depth, int alpha, int beta)
{
    int nowplayer = depth&1;
    if(check(1-nowplayer))
        return -1;
    if(sum == 16)
        return 0;
    for(int i = 0; i < 4; i ++)
        for(int j = 0; j < 4; j ++)
            if(map[i][j] == 2)
            {
                map[i][j] = nowplayer;
                sum ++;
                int tmp = -alpha_beta(depth+1, -beta, -alpha);
                map[i][j] = 2;
                sum --;
                if(tmp >= beta)
                    return beta;
                if(tmp > alpha)
                    alpha = tmp;
                if(depth == 0 && alpha == 1)
                {
                    winx = i, winy = j;
                    return alpha;
                }
            }
    return alpha;
}

int main()
{
    while(getchar() != ‘$‘)
    {
        sum = 0;
        getchar();
        for(int i = 0; i < 4; i ++)
            for(int j = 0; j < 4; j ++)
            {
                c = getchar();
                switch (c){
                    case ‘.‘:
                        map[i][j] = 2;
                        break;
                    case ‘x‘:
                        map[i][j] = 0;
                        sum ++;
                        break;
                    case ‘o‘:
                        map[i][j] = 1;
                        sum ++;
                }
                if(j == 3) getchar();
            }
        if(alpha_beta(0, -INF, INF) == 1)
            printf("(%d,%d)\n", winx, winy);
        else
            printf("#####\n");
    }
    return 0;
}

/*

?
....
.xo.
.ox.
....
?
o...
.ox.
.xxx
xooo
?
xxxo
oxox
....
xxxo
$

*/