LeetCode/rs/maximal-rectangle.rs

use std::cmp;

impl Solution {
    fn indices(rows: usize, cols: usize) -> impl Iterator<Item = (usize, usize)> {
        (0..rows * cols).map(move |i| (i / cols, i % cols))
    }

    fn get(dp: &[Vec<(usize, usize)>], y: usize, x: usize) -> (usize, usize) {
        if y > dp.len() || x > dp[y].len() {
            return (0, 0);
        }

        dp[y][x]
    }

    pub fn maximal_rectangle(matrix: Vec<Vec<char>>) -> i32 {
        let mut found_max = 0;
        let mut dp = vec![vec![(0, 0); matrix[0].len()]; matrix.len()];

        for (y, x) in Self::indices(matrix.len(), matrix[0].len()) {
            if matrix[y][x] != '1' {
                continue;
            }

            let width = 1 + Self::get(&dp, y, x - 1).0;
            let height = 1 + Self::get(&dp, y - 1, x).1;
            dp[y][x] = (width, height);

            found_max = cmp::max(found_max, cmp::max(width, height));

            let mut min_width = width;
            for yy in ((y - height + 1)..y).rev() {
                min_width = cmp::min(min_width, dp[yy][x].0);
                found_max = cmp::max(found_max, min_width * (y - yy + 1));
            }
        }

        found_max.try_into().unwrap()
    }
}