poj 2965 The Pilots Brothers' refrigerator

http://poj.org/problem?id=2965   位运算+搜索

题意：将下图这样的图案都变成减号，规则每次改变一个，这一个的行和列都会发生转换；

思路：总共有2^16的情况，全部都搜一遍，用位运算一次改变一行和一列；

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-+--

搜索题解：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int result = 17;
int path = 0;
int s[16] =
{
    0xf888,0xf444,0xf222,0xf111,
    0x8f88,0x4f44,0x2f22,0x1f11,
    0x88f8,0x44f4,0x22f2,0x11f1,
    0x888f,0x444f,0x222f,0x111f
};
int num = 0;
void search(int d,int step,int q)
{
    if( step >= result)
    return;
    if(d >= 16)
    {
        if(step < result && 0 == num)
        {
            result = step;
            path = q;
        }
        return ;
    }
    q= q << 1;
    q++;
    num = num ^ s[d];
    search(d + 1, step+1, q);
    num = num ^ s[d];
    q--;
    search(d + 1, step, q);
    q = q >>1;
}
void output()
{
    int bit = 15;
    printf("%d\n",result);
    for(int i = 1; i <= 4; ++i)
    for(int j = 1; j <= 4; ++j)
    {
    if((path >> bit)&1)
    printf("%d %d\n",i,j);
    bit--;
    }
}
int main()
{
    char a;
    for(int i = 0;i < 16; ++i)
    {
        a=getchar();
        if('+' == a || '-' == a)
        {
        num = num << 1;
        if('+' == a)
        num++;
        }
        else
        i--;
    }
    search(0,0,0);
    output();
    return 0;
}

简便题解：

#include <cstdio>
#include <algorithm>
#include <string>
#include <iostream>
#include <cstdlib>
using namespace std;
int map[4][4] = {0};
int ji[4][4] = {0};
void bian(int a,int b)
{
    for(int i = 0;i < 4;++i)
    map[a][i] = !map[a][i];
    for(int i = 0;i <4;++i)
    map[i][b] = !map[i][b];
}
int main()
{
    char a;
    for(int i = 0;i < 4;++i)
    {
    for(int j =0;j < 4 ;++j)
    {
        scanf("%c",&a);
        if('+' == a)
        map[i][j] = 1;
    }
    getchar();
    }
  for(int i = 0;i < 4;++i)
  for(int j= 0;j < 4; ++j)
  if(1 == map[i][j])
  ji[i][j] = 1;
  for(int i = 0;i < 4;++i)
  for(int j = 0;j < 4;++j)
  if(ji[i][j])
  bian(i,j);
  int num = 0;
  for(int i = 0;i <4;++i)
  for(int j = 0;j <4;++j)
  if(map[i][j])
  ++num;
  printf("%d\n",num);
  for(int i = 0;i <4;++i)
  for(int j = 0;j <4;++j)
  if(map[i][j])
  printf("%d %d\n",i+1,j+1);
    return 0;
}