Add problem 3153: Sum of Digit Differences of All Pairs

Author: EFanZh

src/lib.rs

@@ -2110,6 +2110,7 @@ pub mod problem_3147_taking_maximum_energy_from_the_mystic_dungeon;
 pub mod problem_3148_maximum_difference_score_in_a_grid;
 pub mod problem_3151_special_array_i;
 pub mod problem_3152_special_array_ii;
+pub mod problem_3153_sum_of_digit_differences_of_all_pairs;
 pub mod problem_3350_adjacent_increasing_subarrays_detection_ii;
 
 #[cfg(test)]

src/problem_3153_sum_of_digit_differences_of_all_pairs/iterative.rs

@@ -0,0 +1,51 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn sum_digit_differences(nums: Vec<i32>) -> i64 {
+        let nums = nums.into_iter().map(i32::cast_unsigned).collect::<Vec<_>>();
+        let mut cache = [(0_u32, [0_u32; 10]); 10];
+
+        let cache = nums
+            .first()
+            .copied()
+            .and_then(|first| cache.get_mut(..first.checked_ilog10()? as usize + 1))
+            .unwrap_or(&mut []);
+
+        let mut result = 0;
+
+        for mut num in nums {
+            for (total, details) in &mut *cache {
+                let digit = num % 10;
+
+                num /= 10;
+
+                let digit = digit as usize;
+                let digit_count = &mut details[digit];
+
+                result += u64::from(*total - *digit_count);
+                *total += 1;
+                *digit_count += 1;
+            }
+        }
+
+        result.cast_signed()
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn sum_digit_differences(nums: Vec<i32>) -> i64 {
+        Self::sum_digit_differences(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3153_sum_of_digit_differences_of_all_pairs/iterative_2.rs

@@ -0,0 +1,44 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn sum_digit_differences(nums: Vec<i32>) -> i64 {
+        let mut nums = nums.into_iter().map(i32::cast_unsigned).collect::<Vec<_>>();
+        let digits = nums.first().copied().and_then(u32::checked_ilog10).map_or(0, |x| x + 1);
+        let mut result = 0;
+
+        for _ in 0..digits {
+            let mut cache = [0_u32; 10];
+
+            (0..).zip(&mut nums).for_each(|(total, num)| {
+                let digit = *num % 10;
+
+                *num /= 10;
+
+                let digit_count = &mut cache[digit as usize];
+
+                result += u64::from(total - *digit_count);
+                *digit_count += 1;
+            });
+        }
+
+        result.cast_signed()
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn sum_digit_differences(nums: Vec<i32>) -> i64 {
+        Self::sum_digit_differences(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3153_sum_of_digit_differences_of_all_pairs/mod.rs

@@ -0,0 +1,19 @@
+pub mod iterative;
+pub mod iterative_2;
+
+pub trait Solution {
+    fn sum_digit_differences(nums: Vec<i32>) -> i64;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(&[13, 23, 12] as &[_], 4), (&[10, 10, 10, 10], 0)];
+
+        for (nums, expected) in test_cases {
+            assert_eq!(S::sum_digit_differences(nums.to_vec()), expected);
+        }
+    }
+}