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| 1 | +class Solution { |
| 2 | + fun maximalRectangle(matrix: Array<CharArray>): Int { |
| 3 | + if (matrix.isEmpty() || matrix[0].isEmpty()) { |
| 4 | + return 0 |
| 5 | + } |
| 6 | + val heights = IntArray(matrix[0].size) |
| 7 | + var maxArea = 0 |
| 8 | + for (row in matrix) { |
| 9 | + for ((index, cell) in row.withIndex()) { |
| 10 | + heights[index] = if (cell == '1') heights[index] + 1 else 0 |
| 11 | + } |
| 12 | + maxArea = maxOf(maxArea, maxRectangleInHistogram(heights)) |
| 13 | + } |
| 14 | + return maxArea |
| 15 | + } |
| 16 | + fun maxRectangleInHistogram(heights: IntArray): Int { |
| 17 | + val stack = mutableListOf<Int>() |
| 18 | + var index = 0 |
| 19 | + var maxArea = 0 |
| 20 | + |
| 21 | + while (index < heights.size) { |
| 22 | + if (stack.isEmpty() || heights[index] >= heights[stack.last()]) { |
| 23 | + stack.add(index++) |
| 24 | + } else { |
| 25 | + val top = stack.removeAt(stack.size - 1) |
| 26 | + val width = if (stack.isEmpty()) index else index - stack.last() - 1 |
| 27 | + maxArea = maxOf(maxArea, heights[top] * width) |
| 28 | + } |
| 29 | + } |
| 30 | + while (stack.isNotEmpty()) { |
| 31 | + val top = stack.removeAt(stack.size - 1) |
| 32 | + val width = if (stack.isEmpty()) index else index - stack.last() - 1 |
| 33 | + maxArea = maxOf(maxArea, heights[top] * width) |
| 34 | + } |
| 35 | + return maxArea |
| 36 | + } |
| 37 | +} |
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