leetcode 85. 最大矩形 golang实现

描述

给定一个仅包含 0 和 1 的二维二进制矩阵，找出只包含 1 的最大矩形，并返回其面积。

示例:

输入:
[
  ["1","0","1","0","0"],
  ["1","0","1","1","1"],
  ["1","1","1","1","1"],
  ["1","0","0","1","0"]
]
输出: 6

思路

84题链接地址

利用84题, 求最大矩形的思想 对每一行求出柱形图的高度

实现

// 85 最大矩形
func maximalRectangle(matrix [][]byte) int {
	var max int
	rows := len(matrix)
	if rows == 0{
		return max
	}

	cols := len(matrix[0])
	nums := make([]int, cols)


	for row := 0; row < rows; row++{
		for col := 0; col < cols; col++{
			if matrix[row][col] != '0'{
				nums[col] = nums[col] + 1
			}else{
				nums[col] = 0
			}
		}

		maxArea := largestRectangleArea(nums)
		max = Max(max, maxArea)
	}

	return max
}

// 84 柱状图中最大的矩形
func largestRectangleArea(heights []int) int {
	var max int
	var stack = make([]int, 0)
	var nums = make([]int, 0)

	nums = append(nums, []int{0}...)
	nums = append(nums, heights...)
	nums = append(nums, []int{0}...)

	for i := 0; i < len(nums); i++{
		for len(stack) > 0 && nums[stack[len(stack)-1]] > nums[i]{
			tmp := stack[len(stack)-1]
			stack = stack[0: len(stack)-1]

			max = Max(max, nums[tmp]*(i-stack[len(stack)-1]-1))
		}

		stack = append(stack, i)
	}

	return max
}

func Max(a, b int) int {
	if a >= b {
		return a
	} else {
		return b
	}
}