洛谷P1879 [USACO06NOV]Corn Fields G

纪念自己第一次理解状压dp写出来的

详解在注释中

//#pragma GCC optimize(3, "Ofast", "inline")
#include <bits/stdc++.h>
using namespace std;
#define debug(x) cout << "*" << x << endl;
#define IOS ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define lowbit(x) x &(-x);
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef unsigned int ui;        /// 0~(2^32)-1
typedef unsigned long long ull; ///0~(2^64)-1
const int inf = 0x3f3f3f3f;
const double eps = 1e-9;
const int P = 131; ///或者P=13331
const int N = 1e5 + 100;
const int M = 2e6 + 7;
const int mod = 100000000;
// #define int ll ///define后面不需要“;”
int n, m, res;
int dp[20][1 << 20], mp[1 << 20];
void AC()
{
    cin >> m >> n;
    for (int i = 1; i <= m; i++)
        for (int j = 1; j <= n; j++)
        {
            int x;
            cin >> x;
            mp[i] |= (x << (n - j));///看成正的二进制数
            // mp[i] |= (x << (j - 1));///看成反的二进制数
        }
    for (int i = 0; i < (1 << n); i++)
    {
        if ((i & (i << 1)) || (i & (i >> 1)))
            continue;
        if ((mp[1] | i) != mp[1]) ///
            continue;
        dp[1][i] = 1;
    }
    for (int i = 2; i <= m; i++) ///
    {
        for (int j = 0; j < (1 << n); j++) ///
        {
            if ((j & (j << 1)) || (j & (j >> 1)))
                continue;
            if ((mp[i] | j) != mp[i])
                continue;
            for (int k = 0; k < (1 << n); k++)
            {
                if ((k & (k << 1)) || (k & (k >> 1)))
                    continue;
                if ((mp[i - 1] | k) != mp[i - 1])
                    continue;
                // if (j & k)
                //     continue;
                // dp[i][j] += dp[i - 1][k];
                // dp[i][j] %= mod;
                if ((j & k) == 0) ///注意位运算的优先级焯
                {
                    dp[i][j] += dp[i - 1][k];
                    dp[i][j] %= mod;
                }
            }
        }
    }
    for (int i = 0; i < (1 << n); i++)
    {
        res += dp[m][i];
        res %= mod;
    }
    cout << res << endl;
}
signed main() ///必须返回int类型
{
    IOS;
    // freopen("T:\\in.txt", "r", stdin);
    // freopen("T:\\out.txt", "w", stdout);
    int _ = 1;
    while (_--)
        AC();
    fclose(stdin);
    fclose(stdout);
    return 0;
}
///      |\_/|
///      | @ @   Woof!
///      |   <>              _
///      |  _/\------____ ((| |))
///      |               `--' |
///  ____|_       ___|   |___.'
/// /_/_____/____/_______|
/// I am here to guard this code, woof!