diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README.md b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README.md index 71ff197a8e287..879eaea0f921c 100644 --- a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README.md +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README.md @@ -48,6 +48,24 @@ +**方法一:状态压缩 + 动态规划** + +我们注意到,网格的行数不超过 $5$,那么一列中最多有 $3^5=243$ 种不同的颜色方案。 + +因此,我们定义 $f[i][j]$ 表示前 $i$ 列中,第 $i$ 列的涂色状态为 $j$ 的方案数。状态 $f[i][j]$ 由 $f[i - 1][k]$ 转移而来,其中 $k$ 是第 $i - 1$ 列的涂色状态,且 $k$ 和 $j$ 满足不同颜色相邻的要求。即: + +$$ +f[i][j] = \sum_{k \in \text{valid}(j)} f[i - 1][k] +$$ + +其中 $\text{valid}(j)$ 表示状态 $j$ 的所有合法前驱状态。 + +最终的答案即为 $f[n][j]$ 的总和,其中 $j$ 是任意合法的状态。 + +我们注意到,$f[i][j]$ 只和 $f[i - 1][k]$ 有关,因此我们可以使用滚动数组优化空间复杂度。 + +时间复杂度 $O((m + n) \times 3^{2m})$,空间复杂度 $O(3^m)$。其中 $m$ 和 $n$ 分别是网格的行数和列数。 + ### **Python3** @@ -55,7 +73,40 @@ ```python +class Solution: + def colorTheGrid(self, m: int, n: int) -> int: + def f1(x: int) -> bool: + last = -1 + for _ in range(m): + if x % 3 == last: + return False + last = x % 3 + x //= 3 + return True + + def f2(x: int, y: int) -> bool: + for _ in range(m): + if x % 3 == y % 3: + return False + x, y = x // 3, y // 3 + return True + mod = 10**9 + 7 + mx = 3**m + valid = {i for i in range(mx) if f1(i)} + d = defaultdict(list) + for x in valid: + for y in valid: + if f2(x, y): + d[x].append(y) + f = [int(i in valid) for i in range(mx)] + for _ in range(n - 1): + g = [0] * mx + for i in valid: + for j in d[i]: + g[i] = (g[i] + f[j]) % mod + f = g + return sum(f) % mod ``` ### **Java** @@ -63,7 +114,263 @@ ```java +class Solution { + private int m; + + public int colorTheGrid(int m, int n) { + this.m = m; + final int mod = (int) 1e9 + 7; + int mx = (int) Math.pow(3, m); + Set valid = new HashSet<>(); + for (int i = 0; i < mx; ++i) { + if (f1(i)) { + valid.add(i); + } + } + Map> d = new HashMap<>(); + for (int i : valid) { + for (int j : valid) { + if (f2(i, j)) { + d.computeIfAbsent(i, k -> new ArrayList<>()).add(j); + } + } + } + int[] f = new int[mx]; + for (int i = 0; i < mx; ++i) { + f[i] = valid.contains(i) ? 1 : 0; + } + for (int k = 1; k < n; ++k) { + int[] g = new int[mx]; + for (int i : valid) { + for (int j : d.getOrDefault(i, List.of())) { + g[i] = (g[i] + f[j]) % mod; + } + } + f = g; + } + int ans = 0; + for (int x : f) { + ans = (ans + x) % mod; + } + return ans; + } + + private boolean f1(int x) { + int last = -1; + for (int i = 0; i < m; ++i) { + if (x % 3 == last) { + return false; + } + last = x % 3; + x /= 3; + } + return true; + } + + private boolean f2(int x, int y) { + for (int i = 0; i < m; ++i) { + if (x % 3 == y % 3) { + return false; + } + x /= 3; + y /= 3; + } + return true; + } +} +``` + +### **C++** + +```cpp +class Solution { +public: + int colorTheGrid(int m, int n) { + auto f1 = [&](int x) { + int last = -1; + for (int i = 0; i < m; ++i) { + if (x % 3 == last) { + return false; + } + last = x % 3; + x /= 3; + } + return true; + }; + auto f2 = [&](int x, int y) { + for (int i = 0; i < m; ++i) { + if (x % 3 == y % 3) { + return false; + } + x /= 3; + y /= 3; + } + return true; + }; + + const int mod = 1e9 + 7; + int mx = pow(3, m); + unordered_set valid; + for (int i = 0; i < mx; ++i) { + if (f1(i)) { + valid.insert(i); + } + } + unordered_map> d; + for (int i : valid) { + for (int j : valid) { + if (f2(i, j)) { + d[i].push_back(j); + } + } + } + vector f(mx); + for (int i = 0; i < mx; ++i) { + f[i] = valid.count(i); + } + for (int k = 1; k < n; ++k) { + vector g(mx); + for (int i : valid) { + for (int j : d[i]) { + g[i] = (g[i] + f[j]) % mod; + } + } + f = move(g); + } + int ans = 0; + for (int x : f) { + ans = (ans + x) % mod; + } + return ans; + } +}; +``` + +### **Go** + +```go +func colorTheGrid(m int, n int) (ans int) { + f1 := func(x int) bool { + last := -1 + for i := 0; i < m; i++ { + if x%3 == last { + return false + } + last = x % 3 + x /= 3 + } + return true + } + f2 := func(x, y int) bool { + for i := 0; i < m; i++ { + if x%3 == y%3 { + return false + } + x /= 3 + y /= 3 + } + return true + } + mx := int(math.Pow(3, float64(m))) + valid := map[int]bool{} + for i := 0; i < mx; i++ { + if f1(i) { + valid[i] = true + } + } + d := map[int][]int{} + for i := range valid { + for j := range valid { + if f2(i, j) { + d[i] = append(d[i], j) + } + } + } + f := make([]int, mx) + for i := 0; i < mx; i++ { + if valid[i] { + f[i] = 1 + } + } + const mod int = 1e9 + 7 + for k := 1; k < n; k++ { + g := make([]int, mx) + for i := range valid { + for _, j := range d[i] { + g[i] = (g[i] + f[j]) % mod + } + } + f = g + } + for _, x := range f { + ans = (ans + x) % mod + } + return +} +``` + +### **TypeScript** +```ts +function colorTheGrid(m: number, n: number): number { + const f1 = (x: number): boolean => { + let last = -1; + for (let i = 0; i < m; ++i) { + if (x % 3 === last) { + return false; + } + last = x % 3; + x = Math.floor(x / 3); + } + return true; + }; + const f2 = (x: number, y: number): boolean => { + for (let i = 0; i < m; ++i) { + if (x % 3 === y % 3) { + return false; + } + x = Math.floor(x / 3); + y = Math.floor(y / 3); + } + return true; + }; + const mx = 3 ** m; + const valid = new Set(); + for (let i = 0; i < mx; ++i) { + if (f1(i)) { + valid.add(i); + } + } + const d: Map = new Map(); + for (const i of valid) { + for (const j of valid) { + if (f2(i, j)) { + d.set(i, (d.get(i) || []).concat(j)); + } + } + } + const f: number[] = Array(mx).fill(0); + for (let i = 0; i < mx; ++i) { + if (valid.has(i)) { + f[i] = 1; + } + } + const mod = 10 ** 9 + 7; + for (let k = 1; k < n; ++k) { + const g: number[] = Array(mx).fill(0); + for (const i of valid) { + for (const j of d.get(i) || []) { + g[i] = (g[i] + f[j]) % mod; + } + } + f.splice(0, f.length, ...g); + } + let ans = 0; + for (const x of f) { + ans = (ans + x) % mod; + } + return ans; +} ``` ### **...** diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README_EN.md b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README_EN.md index 123fd90d3fdde..d0448cf1c28d5 100644 --- a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README_EN.md +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/README_EN.md @@ -42,18 +42,325 @@ ## Solutions +**Solution 1: State Compression + Dynamic Programming** + +We notice that the number of rows in the grid does not exceed $5$, so there are at most $3^5=243$ different color schemes in a column. + +Therefore, we define $f[i][j]$ to represent the number of schemes in the first $i$ columns, where the coloring state of the $i$th column is $j$. The state $f[i][j]$ is transferred from $f[i - 1][k]$, where $k$ is the coloring state of the $i - 1$th column, and $k$ and $j$ meet the requirement of different colors being adjacent. That is: + +$$ +f[i][j] = \sum_{k \in \text{valid}(j)} f[i - 1][k] +$$ + +where $\text{valid}(j)$ represents all legal predecessor states of state $j$. + +The final answer is the sum of $f[n][j]$, where $j$ is any legal state. + +We notice that $f[i][j]$ is only related to $f[i - 1][k]$, so we can use a rolling array to optimize the space complexity. + +The time complexity is $O((m + n) \times 3^{2m})$, and the space complexity is $O(3^m)$. Here, $m$ and $n$ are the number of rows and columns of the grid, respectively. + ### **Python3** ```python +class Solution: + def colorTheGrid(self, m: int, n: int) -> int: + def f1(x: int) -> bool: + last = -1 + for _ in range(m): + if x % 3 == last: + return False + last = x % 3 + x //= 3 + return True + + def f2(x: int, y: int) -> bool: + for _ in range(m): + if x % 3 == y % 3: + return False + x, y = x // 3, y // 3 + return True + mod = 10**9 + 7 + mx = 3**m + valid = {i for i in range(mx) if f1(i)} + d = defaultdict(list) + for x in valid: + for y in valid: + if f2(x, y): + d[x].append(y) + f = [int(i in valid) for i in range(mx)] + for _ in range(n - 1): + g = [0] * mx + for i in valid: + for j in d[i]: + g[i] = (g[i] + f[j]) % mod + f = g + return sum(f) % mod ``` ### **Java** ```java +class Solution { + private int m; + + public int colorTheGrid(int m, int n) { + this.m = m; + final int mod = (int) 1e9 + 7; + int mx = (int) Math.pow(3, m); + Set valid = new HashSet<>(); + for (int i = 0; i < mx; ++i) { + if (f1(i)) { + valid.add(i); + } + } + Map> d = new HashMap<>(); + for (int i : valid) { + for (int j : valid) { + if (f2(i, j)) { + d.computeIfAbsent(i, k -> new ArrayList<>()).add(j); + } + } + } + int[] f = new int[mx]; + for (int i = 0; i < mx; ++i) { + f[i] = valid.contains(i) ? 1 : 0; + } + for (int k = 1; k < n; ++k) { + int[] g = new int[mx]; + for (int i : valid) { + for (int j : d.getOrDefault(i, List.of())) { + g[i] = (g[i] + f[j]) % mod; + } + } + f = g; + } + int ans = 0; + for (int x : f) { + ans = (ans + x) % mod; + } + return ans; + } + + private boolean f1(int x) { + int last = -1; + for (int i = 0; i < m; ++i) { + if (x % 3 == last) { + return false; + } + last = x % 3; + x /= 3; + } + return true; + } + + private boolean f2(int x, int y) { + for (int i = 0; i < m; ++i) { + if (x % 3 == y % 3) { + return false; + } + x /= 3; + y /= 3; + } + return true; + } +} +``` + +### **C++** + +```cpp +class Solution { +public: + int colorTheGrid(int m, int n) { + auto f1 = [&](int x) { + int last = -1; + for (int i = 0; i < m; ++i) { + if (x % 3 == last) { + return false; + } + last = x % 3; + x /= 3; + } + return true; + }; + auto f2 = [&](int x, int y) { + for (int i = 0; i < m; ++i) { + if (x % 3 == y % 3) { + return false; + } + x /= 3; + y /= 3; + } + return true; + }; + + const int mod = 1e9 + 7; + int mx = pow(3, m); + unordered_set valid; + for (int i = 0; i < mx; ++i) { + if (f1(i)) { + valid.insert(i); + } + } + unordered_map> d; + for (int i : valid) { + for (int j : valid) { + if (f2(i, j)) { + d[i].push_back(j); + } + } + } + vector f(mx); + for (int i = 0; i < mx; ++i) { + f[i] = valid.count(i); + } + for (int k = 1; k < n; ++k) { + vector g(mx); + for (int i : valid) { + for (int j : d[i]) { + g[i] = (g[i] + f[j]) % mod; + } + } + f = move(g); + } + int ans = 0; + for (int x : f) { + ans = (ans + x) % mod; + } + return ans; + } +}; +``` + +### **Go** + +```go +func colorTheGrid(m int, n int) (ans int) { + f1 := func(x int) bool { + last := -1 + for i := 0; i < m; i++ { + if x%3 == last { + return false + } + last = x % 3 + x /= 3 + } + return true + } + f2 := func(x, y int) bool { + for i := 0; i < m; i++ { + if x%3 == y%3 { + return false + } + x /= 3 + y /= 3 + } + return true + } + mx := int(math.Pow(3, float64(m))) + valid := map[int]bool{} + for i := 0; i < mx; i++ { + if f1(i) { + valid[i] = true + } + } + d := map[int][]int{} + for i := range valid { + for j := range valid { + if f2(i, j) { + d[i] = append(d[i], j) + } + } + } + f := make([]int, mx) + for i := 0; i < mx; i++ { + if valid[i] { + f[i] = 1 + } + } + const mod int = 1e9 + 7 + for k := 1; k < n; k++ { + g := make([]int, mx) + for i := range valid { + for _, j := range d[i] { + g[i] = (g[i] + f[j]) % mod + } + } + f = g + } + for _, x := range f { + ans = (ans + x) % mod + } + return +} +``` + +### **TypeScript** +```ts +function colorTheGrid(m: number, n: number): number { + const f1 = (x: number): boolean => { + let last = -1; + for (let i = 0; i < m; ++i) { + if (x % 3 === last) { + return false; + } + last = x % 3; + x = Math.floor(x / 3); + } + return true; + }; + const f2 = (x: number, y: number): boolean => { + for (let i = 0; i < m; ++i) { + if (x % 3 === y % 3) { + return false; + } + x = Math.floor(x / 3); + y = Math.floor(y / 3); + } + return true; + }; + const mx = 3 ** m; + const valid = new Set(); + for (let i = 0; i < mx; ++i) { + if (f1(i)) { + valid.add(i); + } + } + const d: Map = new Map(); + for (const i of valid) { + for (const j of valid) { + if (f2(i, j)) { + d.set(i, (d.get(i) || []).concat(j)); + } + } + } + const f: number[] = Array(mx).fill(0); + for (let i = 0; i < mx; ++i) { + if (valid.has(i)) { + f[i] = 1; + } + } + const mod = 10 ** 9 + 7; + for (let k = 1; k < n; ++k) { + const g: number[] = Array(mx).fill(0); + for (const i of valid) { + for (const j of d.get(i) || []) { + g[i] = (g[i] + f[j]) % mod; + } + } + f.splice(0, f.length, ...g); + } + let ans = 0; + for (const x of f) { + ans = (ans + x) % mod; + } + return ans; +} ``` ### **...** diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.cpp b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.cpp new file mode 100644 index 0000000000000..8ade9b1ab5a1e --- /dev/null +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.cpp @@ -0,0 +1,61 @@ +class Solution { +public: + int colorTheGrid(int m, int n) { + auto f1 = [&](int x) { + int last = -1; + for (int i = 0; i < m; ++i) { + if (x % 3 == last) { + return false; + } + last = x % 3; + x /= 3; + } + return true; + }; + auto f2 = [&](int x, int y) { + for (int i = 0; i < m; ++i) { + if (x % 3 == y % 3) { + return false; + } + x /= 3; + y /= 3; + } + return true; + }; + + const int mod = 1e9 + 7; + int mx = pow(3, m); + unordered_set valid; + for (int i = 0; i < mx; ++i) { + if (f1(i)) { + valid.insert(i); + } + } + unordered_map> d; + for (int i : valid) { + for (int j : valid) { + if (f2(i, j)) { + d[i].push_back(j); + } + } + } + vector f(mx); + for (int i = 0; i < mx; ++i) { + f[i] = valid.count(i); + } + for (int k = 1; k < n; ++k) { + vector g(mx); + for (int i : valid) { + for (int j : d[i]) { + g[i] = (g[i] + f[j]) % mod; + } + } + f = move(g); + } + int ans = 0; + for (int x : f) { + ans = (ans + x) % mod; + } + return ans; + } +}; \ No newline at end of file diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.go b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.go new file mode 100644 index 0000000000000..3c7da525b45d9 --- /dev/null +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.go @@ -0,0 +1,58 @@ +func colorTheGrid(m int, n int) (ans int) { + f1 := func(x int) bool { + last := -1 + for i := 0; i < m; i++ { + if x%3 == last { + return false + } + last = x % 3 + x /= 3 + } + return true + } + f2 := func(x, y int) bool { + for i := 0; i < m; i++ { + if x%3 == y%3 { + return false + } + x /= 3 + y /= 3 + } + return true + } + mx := int(math.Pow(3, float64(m))) + valid := map[int]bool{} + for i := 0; i < mx; i++ { + if f1(i) { + valid[i] = true + } + } + d := map[int][]int{} + for i := range valid { + for j := range valid { + if f2(i, j) { + d[i] = append(d[i], j) + } + } + } + f := make([]int, mx) + for i := 0; i < mx; i++ { + if valid[i] { + f[i] = 1 + } + } + const mod int = 1e9 + 7 + for k := 1; k < n; k++ { + g := make([]int, mx) + for i := range valid { + for _, j := range d[i] { + g[i] = (g[i] + f[j]) % mod + } + } + f = g + } + for _, x := range f { + ans = (ans + x) % mod + } + return +} \ No newline at end of file diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.java b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.java new file mode 100644 index 0000000000000..0798bd30f5c83 --- /dev/null +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.java @@ -0,0 +1,64 @@ +class Solution { + private int m; + + public int colorTheGrid(int m, int n) { + this.m = m; + final int mod = (int) 1e9 + 7; + int mx = (int) Math.pow(3, m); + Set valid = new HashSet<>(); + for (int i = 0; i < mx; ++i) { + if (f1(i)) { + valid.add(i); + } + } + Map> d = new HashMap<>(); + for (int i : valid) { + for (int j : valid) { + if (f2(i, j)) { + d.computeIfAbsent(i, k -> new ArrayList<>()).add(j); + } + } + } + int[] f = new int[mx]; + for (int i = 0; i < mx; ++i) { + f[i] = valid.contains(i) ? 1 : 0; + } + for (int k = 1; k < n; ++k) { + int[] g = new int[mx]; + for (int i : valid) { + for (int j : d.getOrDefault(i, List.of())) { + g[i] = (g[i] + f[j]) % mod; + } + } + f = g; + } + int ans = 0; + for (int x : f) { + ans = (ans + x) % mod; + } + return ans; + } + + private boolean f1(int x) { + int last = -1; + for (int i = 0; i < m; ++i) { + if (x % 3 == last) { + return false; + } + last = x % 3; + x /= 3; + } + return true; + } + + private boolean f2(int x, int y) { + for (int i = 0; i < m; ++i) { + if (x % 3 == y % 3) { + return false; + } + x /= 3; + y /= 3; + } + return true; + } +} \ No newline at end of file diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.py b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.py new file mode 100644 index 0000000000000..a48a7114ac661 --- /dev/null +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.py @@ -0,0 +1,34 @@ +class Solution: + def colorTheGrid(self, m: int, n: int) -> int: + def f1(x: int) -> bool: + last = -1 + for _ in range(m): + if x % 3 == last: + return False + last = x % 3 + x //= 3 + return True + + def f2(x: int, y: int) -> bool: + for _ in range(m): + if x % 3 == y % 3: + return False + x, y = x // 3, y // 3 + return True + + mod = 10**9 + 7 + mx = 3**m + valid = {i for i in range(mx) if f1(i)} + d = defaultdict(list) + for x in valid: + for y in valid: + if f2(x, y): + d[x].append(y) + f = [int(i in valid) for i in range(mx)] + for _ in range(n - 1): + g = [0] * mx + for i in valid: + for j in d[i]: + g[i] = (g[i] + f[j]) % mod + f = g + return sum(f) % mod diff --git a/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.ts b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.ts new file mode 100644 index 0000000000000..299e7bdf2747d --- /dev/null +++ b/solution/1900-1999/1931.Painting a Grid With Three Different Colors/Solution.ts @@ -0,0 +1,59 @@ +function colorTheGrid(m: number, n: number): number { + const f1 = (x: number): boolean => { + let last = -1; + for (let i = 0; i < m; ++i) { + if (x % 3 === last) { + return false; + } + last = x % 3; + x = Math.floor(x / 3); + } + return true; + }; + const f2 = (x: number, y: number): boolean => { + for (let i = 0; i < m; ++i) { + if (x % 3 === y % 3) { + return false; + } + x = Math.floor(x / 3); + y = Math.floor(y / 3); + } + return true; + }; + const mx = 3 ** m; + const valid = new Set(); + for (let i = 0; i < mx; ++i) { + if (f1(i)) { + valid.add(i); + } + } + const d: Map = new Map(); + for (const i of valid) { + for (const j of valid) { + if (f2(i, j)) { + d.set(i, (d.get(i) || []).concat(j)); + } + } + } + const f: number[] = Array(mx).fill(0); + for (let i = 0; i < mx; ++i) { + if (valid.has(i)) { + f[i] = 1; + } + } + const mod = 10 ** 9 + 7; + for (let k = 1; k < n; ++k) { + const g: number[] = Array(mx).fill(0); + for (const i of valid) { + for (const j of d.get(i) || []) { + g[i] = (g[i] + f[j]) % mod; + } + } + f.splice(0, f.length, ...g); + } + let ans = 0; + for (const x of f) { + ans = (ans + x) % mod; + } + return ans; +}