README.md

84. Largest Rectangle in Histogram

Given an array of integers heights representing the histogram's bar height where the width of each bar is 1, return the area of the largest rectangle in the histogram.

Example 1:

Input: heights = [2,1,5,6,2,3]
Output: 10
Explanation: The above is a histogram where width of each bar is 1.
The largest rectangle is shown in the red area, which has an area = 10 units.

Example 2:

Input: heights = [2,4]
Output: 4

Constraints:

• 1 <= heights.length <= 105
• 0 <= heights[i] <= 104

Solutions (Rust)

1. Solution

impl Solution {
    pub fn largest_rectangle_area(heights: Vec<i32>) -> i32 {
        let mut stack = vec![];
        let mut widths = vec![1; heights.len()];
        let mut ret = 0;

        for i in 0..heights.len() {
            while stack.last().unwrap_or(&(0, -1)).1 >= heights[i] {
                stack.pop();
            }

            widths[i] = i as i32 - stack.last().unwrap_or(&(-1, 0)).0;
            stack.push((i as i32, heights[i]));
        }

        stack.clear();

        for i in (0..heights.len()).rev() {
            while stack.last().unwrap_or(&(0, -1)).1 >= heights[i] {
                stack.pop();
            }

            widths[i] += stack.last().unwrap_or(&(heights.len() as i32, 0)).0 - 1 - i as i32;
            stack.push((i as i32, heights[i]));
            ret = ret.max(widths[i] * heights[i]);
        }

        ret
    }
}