# 2023-02-11：给你两个整数 m 和 n 。构造一个 m x n 的网格，其中每个单元格最开始是白色

2023-02-11：给你两个整数 m 和 n 。构造一个 m x n 的网格，其中每个单元格最开始是白色，

1 <= n <= 1000。
1 <= m <= 5。

``````use std::iter::repeat;
fn main() {
let ans3 = color_the_grid(4, 3);
println!("ans3 = {}", ans3);
}

static MOD: i32 = 1000000007;

fn color_the_grid(m: i32, n: i32) -> i32 {
let status = 1 << (m << 1);
let mut dp: Vec<Vec<Vec<i32>>> = repeat(
repeat(repeat(-1).take(status as usize).collect())
.take(m as usize)
.collect(),
)
.take(n as usize)
.collect();
return process(0, 0, 0, n, m, &mut dp);
}

fn process(i: i32, j: i32, s: i32, n: i32, m: i32, dp: &mut Vec<Vec<Vec<i32>>>) -> i32 {
if i == n {
return 1;
}
if j == m {
return process(i + 1, 0, s, n, m, dp);
}
if dp[i as usize][j as usize][s as usize] != -1 {
return dp[i as usize][j as usize][s as usize];
}
let up = (s >> (j * 2)) & 3;
let left = if j == 0 { 0 } else { (s >> ((j - 1) << 1)) & 3 };
let mut ans = 0;
if up != 1 && left != 1 {
ans += process(i, j + 1, (s ^ (up << (j * 2))) | (1 << (j * 2)), n, m, dp);
ans %= MOD;
}
if up != 2 && left != 2 {
ans += process(i, j + 1, (s ^ (up << (j << 1))) | (2 << (j << 1)), n, m, dp);
ans %= MOD;
}
if up != 3 && left != 3 {
ans += process(i, j + 1, (s ^ (up << (j << 1))) | (3 << (j << 1)), n, m, dp);
ans %= MOD;
}
dp[i as usize][j as usize][s as usize] = ans;
return ans;
}
``````

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