poj dfs相關之1753 Flip Game

poj dfs相關之1753 Flip Game

132K 313MS

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
int n, k, ans;
bool IsFind, arr[6][6];
int dir[4][2] = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
bool check()
{
    int i, j, t;
    t = arr[1][1];
    for (i = 1; i <= 4;i++)
    for (j = 1; j <= 4; j++)
    {
        if (t != arr[i][j])
            return false;
    }
    return true;
}
void flip(int row, int col)
{
    int i, x, y;
    arr[row][col] = !arr[row][col];
    for (i = 0; i < 4; i++)
    {
        x = row + dir[i][0];
        y = col + dir[i][1];
        arr[x][y] = !arr[x][y];
    }
}
void dfs(int row,int col,int dep)
{
    if (dep == ans)
    {
        if (check())
            IsFind = true;
        return;
    }
    if (row>4 || col > 4 || IsFind)
        return;

    flip(row, col);
    if (col < 4)
        dfs(row, col + 1, dep + 1);
    else
        dfs(row + 1, 1, dep + 1);
    flip(row, col);
    if (col < 4)
        dfs(row, col + 1, dep);
    else
        dfs(row + 1, 1, dep);
}
int main()
{
    //freopen("1.txt", "r", stdin);
    int i, j, tmp1, tmp2;
    memset(arr, 0, sizeof(arr));
    char tmp[15];
    for (i = 1; i < 5; i++)
    {
        scanf("%s", tmp);
        for (j = 1; j < 5; j++)
        {
            if (tmp[j - 1] == 'b')
                arr[i][j] = 1;
            else if (tmp[j - 1] == 'w')
                arr[i][j] = 0;
        }
    }
    for (i = 0; i <= 16; i++)
    {
        IsFind = false;
        ans = i;
        dfs(1, 1, 0);
        if (IsFind)
            break;
    }
    if(IsFind)
        printf("%d\n", ans);
    else
        printf("Impossible\n");
}

132K 125MS
這個是一個一次性枚舉所有的版本，效率更高

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
int n, k, ans;
bool IsFind, arr[6][6];
int dir[4][2] = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
bool check()
{
    int i, j, t;
    t = arr[1][1];
    for (i = 1; i <= 4;i++)
    for (j = 1; j <= 4; j++)
    {
        if (t != arr[i][j])
            return false;
    }
    return true;
}
void flip(int row, int col)
{
    int i, x, y;
    arr[row][col] = !arr[row][col];
    for (i = 0; i < 4; i++)
    {
        x = row + dir[i][0];
        y = col + dir[i][1];
        arr[x][y] = !arr[x][y];
    }
}
void dfs(int row,int col,int dep)
{
    if (check())
    {
        ans = min(ans, dep);
        return;
    }
    if (row>4 || col > 4 || IsFind)
        return;

    flip(row, col);
    if (col < 4)
        dfs(row, col + 1, dep + 1);
    else
        dfs(row + 1, 1, dep + 1);
    flip(row, col);
    if (col < 4)
        dfs(row, col + 1, dep);
    else
        dfs(row + 1, 1, dep);
}
int main()
{
    freopen("1.txt", "r", stdin);
    int i, j, tmp1, tmp2;
    memset(arr, 0, sizeof(arr));
    char tmp[15];
    for (i = 1; i < 5; i++)
    {
        scanf("%s", tmp);
        for (j = 1; j < 5; j++)
        {
            if (tmp[j - 1] == 'b')
                arr[i][j] = 1;
            else if (tmp[j - 1] == 'w')
                arr[i][j] = 0;
        }
    }
    ans = 17;
    dfs(1, 1, 0);
    if(ans<17)
        printf("%d\n", ans);
    else
        printf("Impossible\n");
}