20240830 finished.

src/problem/mod.rs

@@ -220,3 +220,4 @@ mod p698_partition_to_k_equal_sum_subsets;
 mod p3134_find_the_median_of_the_uniqueness_array;
 mod p3144_minimum_substring_partition_of_equal_character_frequency;
 mod p3142_check_if_grid_satisfies_conditions;
+mod p3153_sum_of_digit_differences_of_all_pairs;

src/problem/p3153_sum_of_digit_differences_of_all_pairs.rs

@@ -0,0 +1,50 @@
+/**
+ * [3153] Sum of Digit Differences of All Pairs
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+impl Solution {
+    pub fn sum_digit_differences(nums: Vec<i32>) -> i64 {
+        let n = nums.len() as i64;
+        let mut result = 0;
+
+        let mut base = 1;
+        loop {
+            if nums[0] / base == 0 {
+                break;
+            }
+
+            let mut map = vec![0; 10];
+            for &num in nums.iter() {
+                let digit = (num / base % 10) as usize;
+                map[digit] += 1;
+            }
+
+            result += map.iter().filter_map(|x| if *x == 0 {
+                None
+            } else {
+                Some(*x * (n - *x))
+            }).sum::<i64>() / 2;
+
+            base *= 10;
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_3153() {
+        assert_eq!(4, Solution::sum_digit_differences(vec![13, 23, 12]));
+        assert_eq!(0, Solution::sum_digit_differences(vec![10, 10, 10, 10]));
+    }
+}