add sol

leetcode/85.MaximalRectangle/sol.go

@@ -0,0 +1,65 @@
+// https://leetcode.com/problems/maximal-rectangle/
+
+package main
+
+import "fmt"
+
+func maximalRectangle(matrix [][]byte) int {
+	n := len(matrix[0])
+	heights := make([]int, n)
+	ans := 0
+	for _, row := range matrix {
+		for j, v := range row {
+			if v == '1' {
+				heights[j]++
+			} else {
+				heights[j] = 0
+			}
+		}
+		ans = max(ans, largestRectangleArea(heights))
+	}
+	return ans
+}
+
+func largestRectangleArea(heights []int) int {
+	res, n := 0, len(heights)
+	var stk []int
+	left, right := make([]int, n), make([]int, n)
+	for i := range right {
+		right[i] = n
+	}
+	for i, h := range heights {
+		for len(stk) > 0 && heights[stk[len(stk)-1]] >= h {
+			right[stk[len(stk)-1]] = i
+			stk = stk[:len(stk)-1]
+		}
+		if len(stk) > 0 {
+			left[i] = stk[len(stk)-1]
+		} else {
+			left[i] = -1
+		}
+		stk = append(stk, i)
+	}
+	for i, h := range heights {
+		res = max(res, h*(right[i]-left[i]-1))
+	}
+	return res
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func main() {
+	matrix := [][]byte{
+		{'1', '0', '1', '0', '0'},
+		{'1', '0', '1', '1', '1'},
+		{'1', '1', '1', '1', '1'},
+		{'1', '0', '0', '1', '0'},
+	}
+
+	fmt.Println(maximalRectangle(matrix))
+}