1937. Maximum Number of Points with Cost: AC

Author: tan-wei

Diff for: src/solution/mod.rs

@@ -1460,3 +1460,4 @@ mod s1931_painting_a_grid_with_three_different_colors;
 mod s1932_merge_bsts_to_create_single_bst;
 mod s1935_maximum_number_of_words_you_can_type;
 mod s1936_add_minimum_number_of_rungs;
+mod s1937_maximum_number_of_points_with_cost;

Diff for: src/solution/s1937_maximum_number_of_points_with_cost.rs

@@ -0,0 +1,101 @@
+/**
+ * [1937] Maximum Number of Points with Cost
+ *
+ * You are given an m x n integer matrix points (0-indexed). Starting with 0 points, you want to maximize the number of points you can get from the matrix.
+ * To gain points, you must pick one cell in each row. Picking the cell at coordinates (r, c) will add points[r][c] to your score.
+ * However, you will lose points if you pick a cell too far from the cell that you picked in the previous row. For every two adjacent rows r and r + 1 (where 0 <= r < m - 1), picking cells at coordinates (r, c1) and (r + 1, c2) will subtract abs(c1 - c2) from your score.
+ * Return the maximum number of points you can achieve.
+ * abs(x) is defined as:
+ *
+ * 	x for x >= 0.
+ * 	-x for x < 0.
+ *
+ *  
+ * Example 1:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/07/12/screenshot-2021-07-12-at-13-40-26-diagram-drawio-diagrams-net.png" style="width: 300px; height: 300px;" />
+ * Input: points = [[1,2,3],[1,5,1],[3,1,1]]
+ * Output: 9
+ * Explanation:
+ * The blue cells denote the optimal cells to pick, which have coordinates (0, 2), (1, 1), and (2, 0).
+ * You add 3 + 5 + 3 = 11 to your score.
+ * However, you must subtract abs(2 - 1) + abs(1 - 0) = 2 from your score.
+ * Your final score is 11 - 2 = 9.
+ *
+ * Example 2:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/07/12/screenshot-2021-07-12-at-13-42-14-diagram-drawio-diagrams-net.png" style="width: 200px; height: 299px;" />
+ * Input: points = [[1,5],[2,3],[4,2]]
+ * Output: 11
+ * Explanation:
+ * The blue cells denote the optimal cells to pick, which have coordinates (0, 1), (1, 1), and (2, 0).
+ * You add 5 + 3 + 4 = 12 to your score.
+ * However, you must subtract abs(1 - 1) + abs(1 - 0) = 1 from your score.
+ * Your final score is 12 - 1 = 11.
+ *
+ *  
+ * Constraints:
+ *
+ * 	m == points.length
+ * 	n == points[r].length
+ * 	1 <= m, n <= 10^5
+ * 	1 <= m * n <= 10^5
+ * 	0 <= points[r][c] <= 10^5
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/maximum-number-of-points-with-cost/
+// discuss: https://leetcode.com/problems/maximum-number-of-points-with-cost/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn max_points(points: Vec<Vec<i32>>) -> i64 {
+        let mut points = points;
+
+        let mut prev = points
+            .pop()
+            .unwrap()
+            .into_iter()
+            .map(i64::from)
+            .collect::<Vec<_>>();
+
+        while let Some(next) = points.pop() {
+            prev.iter_mut().rfold(0, |adj, cur| {
+                *cur = (adj - 1).max(*cur);
+                *cur
+            });
+
+            prev.iter_mut().zip(next).fold(0, |adj, (cur, next)| {
+                let new_adj = (adj - 1).max(*cur);
+                *cur = new_adj + next as i64;
+                new_adj
+            });
+        }
+        prev.into_iter().max().unwrap()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1937_example_1() {
+        let points = vec![vec![1, 2, 3], vec![1, 5, 1], vec![3, 1, 1]];
+
+        let result = 9;
+
+        assert_eq!(Solution::max_points(points), result);
+    }
+
+    #[test]
+    fn test_1937_example_2() {
+        let points = vec![vec![1, 5], vec![2, 3], vec![4, 2]];
+
+        let result = 11;
+
+        assert_eq!(Solution::max_points(points), result);
+    }
+}