|
| 1 | +--- |
| 2 | +comments: true |
| 3 | +difficulty: 困难 |
| 4 | +edit_url: https://github.com/doocs/leetcode/edit/main/solution/3800-3899/3888.Minimum%20Operations%20to%20Make%20All%20Grid%20Elements%20Equal/README.md |
| 5 | +--- |
| 6 | + |
| 7 | +<!-- problem:start --> |
| 8 | + |
| 9 | +# [3888. Minimum Operations to Make All Grid Elements Equal 🔒](https://leetcode.cn/problems/minimum-operations-to-make-all-grid-elements-equal) |
| 10 | + |
| 11 | +[English Version](/solution/3800-3899/3888.Minimum%20Operations%20to%20Make%20All%20Grid%20Elements%20Equal/README_EN.md) |
| 12 | + |
| 13 | +## 题目描述 |
| 14 | + |
| 15 | +<!-- description:start --> |
| 16 | + |
| 17 | +<p>You are given a 2D integer array <code>grid</code> of size <code>m × n</code>, and an integer <code>k</code>.</p> |
| 18 | + |
| 19 | +<p>In one operation, you can:</p> |
| 20 | + |
| 21 | +<ul> |
| 22 | + <li>Select any <code>k x k</code> <strong>submatrix</strong> of <code>grid</code>, and</li> |
| 23 | + <li>Increment <strong>all elements</strong> inside that <strong>submatrix</strong> by 1.</li> |
| 24 | +</ul> |
| 25 | + |
| 26 | +<p>Return the <strong>minimum</strong> number of operations required to make all elements in the grid <strong>equal</strong>. If it is not possible, return -1.</p> |
| 27 | +A submatrix <code>(x1, y1, x2, y2)</code> is a matrix that forms by choosing all cells <code>matrix[x][y]</code> where <code>x1 <= x <= x2</code> and <code>y1 <= y <= y2</code>. |
| 28 | +<p> </p> |
| 29 | +<p><strong class="example">Example 1:</strong></p> |
| 30 | + |
| 31 | +<div class="example-block"> |
| 32 | +<p><strong>Input:</strong> <span class="example-io">grid = [[3,3,5],[3,3,5]], k = 2</span></p> |
| 33 | + |
| 34 | +<p><strong>Output:</strong> <span class="example-io">2</span></p> |
| 35 | + |
| 36 | +<p><strong>Explanation:</strong></p> |
| 37 | + |
| 38 | +<p data-end="266" data-start="150">Choose the left <code>2 x 2</code> submatrix (covering the first two columns) and apply the operation twice.</p> |
| 39 | + |
| 40 | +<ul> |
| 41 | + <li>After 1 operation: <code>[[4, 4, 5], [4, 4, 5]]</code></li> |
| 42 | + <li>After 2 operations: <code>[[5, 5, 5], [5, 5, 5]]</code></li> |
| 43 | +</ul> |
| 44 | + |
| 45 | +<p>All elements become equal to 5. Thus, the minimum number of operations is 2.</p> |
| 46 | +</div> |
| 47 | + |
| 48 | +<p><strong class="example">Example 2:</strong></p> |
| 49 | + |
| 50 | +<div class="example-block"> |
| 51 | +<p><strong>Input:</strong> <span class="example-io">grid = [[1,2],[2,3]], k = 1</span></p> |
| 52 | + |
| 53 | +<p><strong>Output:</strong> <span class="example-io">4</span></p> |
| 54 | + |
| 55 | +<p><strong>Explanation:</strong></p> |
| 56 | + |
| 57 | +<p>Since <code>k = 1</code>, each operation increments a single cell <code>grid[i][j]</code> by 1. To make all elements equal, the final value must be 3.</p> |
| 58 | + |
| 59 | +<ul> |
| 60 | + <li>Increase <code>grid[0][0] = 1</code> to 3, requiring 2 operations.</li> |
| 61 | + <li>Increase <code>grid[0][1] = 2</code> to 3, requiring 1 operation.</li> |
| 62 | + <li>Increase <code>grid[1][0] = 2</code> to 3, requiring 1 operation.</li> |
| 63 | +</ul> |
| 64 | + |
| 65 | +<p>Thus, the minimum number of operations is <code>2 + 1 + 1 + 0 = 4</code>.</p> |
| 66 | +</div> |
| 67 | + |
| 68 | +<p> </p> |
| 69 | +<p><strong>Constraints:</strong></p> |
| 70 | + |
| 71 | +<ul> |
| 72 | + <li><code>1 <= m == grid.length <= 1000</code></li> |
| 73 | + <li><code>1 <= n == grid[i].length <= 1000</code></li> |
| 74 | + <li><code>-10<sup>5</sup> <= grid[i][j] <= 10<sup>5</sup></code></li> |
| 75 | + <li><code>1 <= k <= min(m, n)</code></li> |
| 76 | +</ul> |
| 77 | + |
| 78 | +<!-- description:end --> |
| 79 | + |
| 80 | +## 解法 |
| 81 | + |
| 82 | +<!-- solution:start --> |
| 83 | + |
| 84 | +### 方法一:二维差分 + 贪心 |
| 85 | + |
| 86 | +由于操作只能增加元素的值,因此最终网格的所有元素必须等于某个目标值 $T$,且 $T \ge \max(\textit{grid})$。 |
| 87 | + |
| 88 | +从左上角 $(0, 0)$ 开始遍历网格。对于任意位置 $(i, j)$,如果它当前的数值小于 $T$,由于后续的操作(以更靠右或更靠下的位置为左上角的操作)都无法覆盖到 $(i, j)$,因此必须在当前位置执行 $T - \text{current\_val}$ 次以 $(i, j)$ 为左上角的 $k \times k$ 增加操作。 |
| 89 | + |
| 90 | +如果每次执行操作都遍历 $k \times k$ 区域,复杂度将达到 $O(m \cdot n \cdot k^2)$。我们可以使用二维差分数组 $\textit{diff}$ 来记录操作。通过实时维护 $\textit{diff}$ 的二维前缀和,我们可以在 $O(1)$ 时间内获取当前位置的累计增量,并在 $O(1)$ 时间内更新一个 $k \times k$ 区域的未来影响。 |
| 91 | + |
| 92 | +通常情况下 $T = \max(\textit{grid})$ 即可。但在某些 $k \times k$ 覆盖重叠的情况下,较小的 $T$ 可能导致中间位置被动增加后超过 $T$。根据数学一致性,若 $T = \max(\textit{grid})$ 和 $T = \max(\textit{grid}) + 1$ 均不可行,则该网格无法通过 $k \times k$ 操作变平。 |
| 93 | + |
| 94 | +时间复杂度 $O(m \times n)$,空间复杂度 $O(m \times n)$,其中 $m$ 和 $n$ 分别是网格的行数和列数。 |
| 95 | + |
| 96 | +<!-- tabs:start --> |
| 97 | + |
| 98 | +#### Python3 |
| 99 | + |
| 100 | +```python |
| 101 | +class Solution: |
| 102 | + def minOperations(self, grid: list[list[int]], k: int) -> int: |
| 103 | + m, n = len(grid), len(grid[0]) |
| 104 | + mx = max(max(row) for row in grid) |
| 105 | + |
| 106 | + def check(target: int) -> int: |
| 107 | + diff = [[0] * (n + 2) for _ in range(m + 2)] |
| 108 | + total_ops = 0 |
| 109 | + |
| 110 | + for i, row in enumerate(grid, 1): |
| 111 | + for j, val in enumerate(row, 1): |
| 112 | + diff[i][j] += diff[i - 1][j] + diff[i][j - 1] - diff[i - 1][j - 1] |
| 113 | + |
| 114 | + cur_val = val + diff[i][j] |
| 115 | + |
| 116 | + if cur_val > target: |
| 117 | + return -1 |
| 118 | + |
| 119 | + if cur_val < target: |
| 120 | + if i + k - 1 > m or j + k - 1 > n: |
| 121 | + return -1 |
| 122 | + |
| 123 | + needed = target - cur_val |
| 124 | + total_ops += needed |
| 125 | + diff[i][j] += needed |
| 126 | + diff[i + k][j] -= needed |
| 127 | + diff[i][j + k] -= needed |
| 128 | + diff[i + k][j + k] += needed |
| 129 | + return total_ops |
| 130 | + |
| 131 | + for t in range(mx, mx + 2): |
| 132 | + res = check(t) |
| 133 | + if res != -1: |
| 134 | + return res |
| 135 | + |
| 136 | + return -1 |
| 137 | +``` |
| 138 | + |
| 139 | +#### Java |
| 140 | + |
| 141 | +```java |
| 142 | +class Solution { |
| 143 | + int[][] grid; |
| 144 | + int m, n, k; |
| 145 | + |
| 146 | + public long minOperations(int[][] grid, int k) { |
| 147 | + this.grid = grid; |
| 148 | + this.k = k; |
| 149 | + this.m = grid.length; |
| 150 | + this.n = grid[0].length; |
| 151 | + |
| 152 | + int mx = Integer.MIN_VALUE; |
| 153 | + for (int[] row : grid) { |
| 154 | + for (int v : row) { |
| 155 | + mx = Math.max(mx, v); |
| 156 | + } |
| 157 | + } |
| 158 | + |
| 159 | + for (int t = mx; t <= mx + 1; t++) { |
| 160 | + long res = check(t); |
| 161 | + if (res != -1) { |
| 162 | + return res; |
| 163 | + } |
| 164 | + } |
| 165 | + return -1; |
| 166 | + } |
| 167 | + |
| 168 | + private long check(int target) { |
| 169 | + long[][] diff = new long[m + 2][n + 2]; |
| 170 | + long totalOps = 0; |
| 171 | + |
| 172 | + for (int i = 1; i <= m; i++) { |
| 173 | + for (int j = 1; j <= n; j++) { |
| 174 | + diff[i][j] += diff[i - 1][j] + diff[i][j - 1] - diff[i - 1][j - 1]; |
| 175 | + long cur = grid[i - 1][j - 1] + diff[i][j]; |
| 176 | + |
| 177 | + if (cur > target) { |
| 178 | + return -1; |
| 179 | + } |
| 180 | + |
| 181 | + if (cur < target) { |
| 182 | + if (i + k - 1 > m || j + k - 1 > n) { |
| 183 | + return -1; |
| 184 | + } |
| 185 | + |
| 186 | + long need = target - cur; |
| 187 | + totalOps += need; |
| 188 | + |
| 189 | + diff[i][j] += need; |
| 190 | + diff[i + k][j] -= need; |
| 191 | + diff[i][j + k] -= need; |
| 192 | + diff[i + k][j + k] += need; |
| 193 | + } |
| 194 | + } |
| 195 | + } |
| 196 | + return totalOps; |
| 197 | + } |
| 198 | +} |
| 199 | +``` |
| 200 | + |
| 201 | +#### C++ |
| 202 | + |
| 203 | +```cpp |
| 204 | +class Solution { |
| 205 | +public: |
| 206 | + long long minOperations(vector<vector<int>>& grid, int k) { |
| 207 | + int m = grid.size(); |
| 208 | + int n = grid[0].size(); |
| 209 | + int mx = grid[0][0]; |
| 210 | + for (auto& row : grid) { |
| 211 | + for (int val : row) { |
| 212 | + mx = max(mx, val); |
| 213 | + } |
| 214 | + } |
| 215 | + |
| 216 | + auto check = [&](int target) -> long long { |
| 217 | + vector<vector<long long>> diff(m + 2, vector<long long>(n + 2, 0)); |
| 218 | + long long total_ops = 0; |
| 219 | + |
| 220 | + for (int i = 1; i <= m; ++i) { |
| 221 | + for (int j = 1; j <= n; ++j) { |
| 222 | + diff[i][j] += diff[i - 1][j] + diff[i][j - 1] - diff[i - 1][j - 1]; |
| 223 | + long long cur_val = grid[i - 1][j - 1] + diff[i][j]; |
| 224 | + |
| 225 | + if (cur_val > target) { |
| 226 | + return -1; |
| 227 | + } |
| 228 | + |
| 229 | + if (cur_val < target) { |
| 230 | + if (i + k - 1 > m || j + k - 1 > n) { |
| 231 | + return -1; |
| 232 | + } |
| 233 | + |
| 234 | + long long needed = target - cur_val; |
| 235 | + total_ops += needed; |
| 236 | + diff[i][j] += needed; |
| 237 | + diff[i + k][j] -= needed; |
| 238 | + diff[i][j + k] -= needed; |
| 239 | + diff[i + k][j + k] += needed; |
| 240 | + } |
| 241 | + } |
| 242 | + } |
| 243 | + |
| 244 | + return total_ops; |
| 245 | + }; |
| 246 | + |
| 247 | + for (int t = mx; t <= mx + 1; ++t) { |
| 248 | + long long res = check(t); |
| 249 | + if (res != -1) { |
| 250 | + return res; |
| 251 | + } |
| 252 | + } |
| 253 | + |
| 254 | + return -1; |
| 255 | + } |
| 256 | +}; |
| 257 | +``` |
| 258 | + |
| 259 | +#### Go |
| 260 | + |
| 261 | +```go |
| 262 | +func minOperations(grid [][]int, k int) int64 { |
| 263 | + m, n := len(grid), len(grid[0]) |
| 264 | + maxVal := grid[0][0] |
| 265 | + for _, row := range grid { |
| 266 | + maxVal = max(maxVal, slices.Max(row)) |
| 267 | + } |
| 268 | + |
| 269 | + check := func(target int) int64 { |
| 270 | + diff := make([][]int64, m+2) |
| 271 | + for i := range diff { |
| 272 | + diff[i] = make([]int64, n+2) |
| 273 | + } |
| 274 | + var totalOps int64 |
| 275 | + |
| 276 | + for i := 1; i <= m; i++ { |
| 277 | + for j := 1; j <= n; j++ { |
| 278 | + diff[i][j] += diff[i-1][j] + diff[i][j-1] - diff[i-1][j-1] |
| 279 | + curVal := int64(grid[i-1][j-1]) + diff[i][j] |
| 280 | + |
| 281 | + if curVal > int64(target) { |
| 282 | + return -1 |
| 283 | + } |
| 284 | + |
| 285 | + if curVal < int64(target) { |
| 286 | + if i+k-1 > m || j+k-1 > n { |
| 287 | + return -1 |
| 288 | + } |
| 289 | + needed := int64(target) - curVal |
| 290 | + totalOps += needed |
| 291 | + diff[i][j] += needed |
| 292 | + diff[i+k][j] -= needed |
| 293 | + diff[i][j+k] -= needed |
| 294 | + diff[i+k][j+k] += needed |
| 295 | + } |
| 296 | + } |
| 297 | + } |
| 298 | + return totalOps |
| 299 | + } |
| 300 | + |
| 301 | + for t := maxVal; t <= maxVal+1; t++ { |
| 302 | + if res := check(t); res != -1 { |
| 303 | + return res |
| 304 | + } |
| 305 | + } |
| 306 | + |
| 307 | + return -1 |
| 308 | +} |
| 309 | +``` |
| 310 | + |
| 311 | +#### TypeScript |
| 312 | + |
| 313 | +```ts |
| 314 | +function minOperations(grid: number[][], k: number): number { |
| 315 | + const m = grid.length; |
| 316 | + const n = grid[0].length; |
| 317 | + let maxVal = grid[0][0]; |
| 318 | + |
| 319 | + for (const row of grid) { |
| 320 | + for (const val of row) { |
| 321 | + maxVal = Math.max(maxVal, val); |
| 322 | + } |
| 323 | + } |
| 324 | + |
| 325 | + const check = (target: number): number => { |
| 326 | + const diff: number[][] = Array.from({ length: m + 2 }, () => Array(n + 2).fill(0)); |
| 327 | + let totalOps = 0; |
| 328 | + |
| 329 | + for (let i = 1; i <= m; i++) { |
| 330 | + for (let j = 1; j <= n; j++) { |
| 331 | + diff[i][j] += diff[i - 1][j] + diff[i][j - 1] - diff[i - 1][j - 1]; |
| 332 | + const curVal = grid[i - 1][j - 1] + diff[i][j]; |
| 333 | + |
| 334 | + if (curVal > target) return -1; |
| 335 | + |
| 336 | + if (curVal < target) { |
| 337 | + if (i + k - 1 > m || j + k - 1 > n) return -1; |
| 338 | + |
| 339 | + const needed = target - curVal; |
| 340 | + totalOps += needed; |
| 341 | + diff[i][j] += needed; |
| 342 | + diff[i + k][j] -= needed; |
| 343 | + diff[i][j + k] -= needed; |
| 344 | + diff[i + k][j + k] += needed; |
| 345 | + } |
| 346 | + } |
| 347 | + } |
| 348 | + |
| 349 | + return totalOps; |
| 350 | + }; |
| 351 | + |
| 352 | + for (let t = maxVal; t <= maxVal + 1; t++) { |
| 353 | + const res = check(t); |
| 354 | + if (res !== -1) return res; |
| 355 | + } |
| 356 | + |
| 357 | + return -1; |
| 358 | +} |
| 359 | +``` |
| 360 | + |
| 361 | +<!-- tabs:end --> |
| 362 | + |
| 363 | +<!-- solution:end --> |
| 364 | + |
| 365 | +<!-- problem:end --> |
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