AC 84

hard/84.go

@@ -1,12 +1,66 @@
 package main
 
-func largestRectangleArea(heights []int) int {
-	return 0
+func largestRectangleAreaSlow(heights []int) (area int) {
+	n := len(heights)
+	if n == 0 {
+		return
+	}
+	for i := 0; i < n; i++ {
+		min := heights[i]
+		for j := i; j < n; j++ {
+			if heights[j] < min {
+				min = heights[j]
+			}
+			if (j-i+1)*min > area {
+				area = (j - i + 1) * min
+			}
+		}
+	}
+	return
 }
 
-func main() {
-	h := []int{2, 1, 5, 6, 2, 3}
-	println(largestRectangleArea(h))
-	h = []int{}
-	println(largestRectangleArea(h))
+func largestRectangleArea(heights []int) (maxArea int) {
+	st := make([]int, 0) // The max area must be between two smaller bar
+	i, l, n := 0, 0, len(heights)
+	for i < n {
+		if l == 0 || heights[i] >= heights[st[l-1]] {
+			st = append(st, i)
+			i, l = i+1, l+1
+		} else {
+			t := st[l-1]
+			st = st[:l-1]
+			l--
+			var area int
+			if l == 0 {
+				area = heights[t] * i
+			} else {
+				area = heights[t] * (i - st[l-1] - 1)
+			}
+			if area > maxArea {
+				maxArea = area
+			}
+		}
+	}
+	for l != 0 {
+		t := st[l-1]
+		st = st[:l-1]
+		l--
+		var area int
+		if l == 0 {
+			area = heights[t] * i
+		} else {
+			area = heights[t] * (i - st[l-1] - 1)
+		}
+		if area > maxArea {
+			maxArea = area
+		}
+	}
+	return
 }
+
+// func main() {
+// 	h := []int{2, 1, 5, 6, 2, 3}
+// 	println(largestRectangleArea(h))
+// 	h = []int{}
+// 	println(largestRectangleArea(h))
+// }

hard/85.go

@@ -0,0 +1,9 @@
+package main
+
+func maximalRectangle(matrix [][]byte) int {
+	return 0
+}
+
+func main() {
+
+}