uva-639-枚举

　题意：

象棋里的車可以吃横竖的車,题目加了一个墙,用于阻断攻击,问4x4的棋盘最多可以放多少只車,

思路:枚举每一个点,2^16次方种情况

#include<stdio.h>
#include<iostream>
#include<sstream>
#include<queue>
#include<map>
#include<memory.h>
#include <math.h>
#include<time.h>
#include <stdlib.h>
#include <algorithm>
using namespace std;
#define N 8
int m[N][N];
int vis[N];
int n;
int final = 0;
void dfs(int curLine, int curCol, int num)
{
    if(curLine > n)
    {
        final = final < num ? num : final;
        return;
    }
    if(m[curLine][curCol] == 2)
    {
        if(curCol + 1 > n)
            dfs(curLine + 1, 1, num);
        else
            dfs(curLine, curCol + 1, num);
        return;
    }
    int ok = 1;
    for(int i = curLine - 1; i >= 1; i--)
    {
        if(m[i][curCol] == 2)
            break;
        if(m[i][curCol] == 1)
        {
            ok = 0;
            break;
        }
    }
    for(int i = curCol - 1; i >= 1&&ok; i--)
    {
        if(m[curLine][i] == 2)
            break;
        if(m[curLine][i] == 1)
        {
            ok = 0;
            break;
        }
    }
    if(ok)
    {
        m[curLine][curCol] = 1;
        if(curCol + 1 > n)
            dfs(curLine + 1, 1, num + 1);
        else
            dfs(curLine, curCol + 1, num + 1);
        m[curLine][curCol] = 0;
    }
    if(curCol + 1 > n)
        dfs(curLine + 1, 1, num);
    else
        dfs(curLine, curCol + 1, num);
}

int main(const int argc, char** argv)
{
    //freopen("d:\\1.txt", "r", stdin);
    while (cin >> n && n)
    {
        final = 0;
        memset(vis, 0, sizeof(vis));
        memset(m, -1, sizeof(m));
        char c;
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
            {
                cin >> c;
                if(c == 'X')
                    m[i][j] = 2;
                else
                    m[i][j] = 0;
            }
        dfs(1, 1, 0);
        cout << final << endl;
    }
    return 0;
}