1742. Maximum Number of Balls in a Box: AC

Author: tan-wei

src/solution/mod.rs

@@ -1312,3 +1312,4 @@ mod s1736_latest_time_by_replacing_hidden_digits;
 mod s1737_change_minimum_characters_to_satisfy_one_of_three_conditions;
 mod s1738_find_kth_largest_xor_coordinate_value;
 mod s1739_building_boxes;
+mod s1742_maximum_number_of_balls_in_a_box;

src/solution/s1742_maximum_number_of_balls_in_a_box.rs

@@ -0,0 +1,101 @@
+/**
+ * [1742] Maximum Number of Balls in a Box
+ *
+ * You are working in a ball factory where you have n balls numbered from lowLimit up to highLimit inclusive (i.e., n == highLimit - lowLimit + 1), and an infinite number of boxes numbered from 1 to infinity.
+ * Your job at this factory is to put each ball in the box with a number equal to the sum of digits of the ball's number. For example, the ball number 321 will be put in the box number 3 + 2 + 1 = 6 and the ball number 10 will be put in the box number 1 + 0 = 1.
+ * Given two integers lowLimit and highLimit, return the number of balls in the box with the most balls.
+ *  
+ * Example 1:
+ *
+ * Input: lowLimit = 1, highLimit = 10
+ * Output: 2
+ * Explanation:
+ * Box Number:  1 2 3 4 5 6 7 8 9 10 11 ...
+ * Ball Count:  2 1 1 1 1 1 1 1 1 0  0  ...
+ * Box 1 has the most number of balls with 2 balls.
+ * Example 2:
+ *
+ * Input: lowLimit = 5, highLimit = 15
+ * Output: 2
+ * Explanation:
+ * Box Number:  1 2 3 4 5 6 7 8 9 10 11 ...
+ * Ball Count:  1 1 1 1 2 2 1 1 1 0  0  ...
+ * Boxes 5 and 6 have the most number of balls with 2 balls in each.
+ *
+ * Example 3:
+ *
+ * Input: lowLimit = 19, highLimit = 28
+ * Output: 2
+ * Explanation:
+ * Box Number:  1 2 3 4 5 6 7 8 9 10 11 12 ...
+ * Ball Count:  0 1 1 1 1 1 1 1 1 2  0  0  ...
+ * Box 10 has the most number of balls with 2 balls.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= lowLimit <= highLimit <= 10^5
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/maximum-number-of-balls-in-a-box/
+// discuss: https://leetcode.com/problems/maximum-number-of-balls-in-a-box/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn count_balls(low_limit: i32, high_limit: i32) -> i32 {
+        let mut boxes = [0; 46];
+        let sum_of_digits = |mut x: i32| {
+            let mut s = 0;
+            while x > 0 {
+                s += x % 10;
+                x /= 10;
+            }
+            s as usize
+        };
+
+        (low_limit..=high_limit).for_each(|val| boxes[sum_of_digits(val)] += 1);
+        boxes.iter().fold(0, |max_val, &x| max_val.max(x))
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use std::result;
+
+    use super::*;
+
+    #[test]
+    fn test_1742_example_1() {
+        let low_limit = 1;
+        let high_limit = 10;
+
+        let result = 2;
+
+        assert_eq!(Solution::count_balls(low_limit, high_limit), result);
+    }
+
+    #[test]
+    fn test_1742_example_2() {
+        let low_limit = 5;
+        let high_limit = 15;
+
+        let result = 2;
+
+        assert_eq!(Solution::count_balls(low_limit, high_limit), result);
+    }
+
+    #[test]
+    fn test_1742_example_3() {
+        let low_limit = 19;
+        let high_limit = 28;
+
+        let result = 2;
+
+        assert_eq!(Solution::count_balls(low_limit, high_limit), result);
+    }
+}