20241212 finished.

src/problem/mod.rs

@@ -364,3 +364,5 @@ mod p1812_determine_color_of_a_chessboard_square;
 mod p935_knight_dialer;
 
 mod p2717_semi_ordered_permutation;
+
+mod p2931_maximum_spending_after_buying_items;

src/problem/p2931_maximum_spending_after_buying_items.rs

@@ -0,0 +1,74 @@
+/**
+ * [2931] Maximum Spending After Buying Items
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::cmp::Ordering;
+use std::collections::BinaryHeap;
+
+#[derive(Debug, PartialEq, Eq)]
+struct Item {
+    price: i64,
+    shop: usize,
+    pos: usize,
+}
+
+impl Ord for Item {
+    fn cmp(&self, other: &Self) -> Ordering {
+        other.price.cmp(&self.price)
+    }
+}
+
+impl PartialOrd for Item {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Solution {
+    pub fn max_spending(values: Vec<Vec<i32>>) -> i64 {
+        let (m, n) = (values.len(), values[0].len());
+        let mut heap = BinaryHeap::with_capacity(values.len());
+        let mut result = 0;
+
+        for i in 0..m {
+            heap.push(Item {
+                price: values[i][n - 1] as i64,
+                shop: i,
+                pos: n - 1,
+            });
+        }
+
+        let mut day = 1;
+        while let Some(top) = heap.pop() {
+            result += top.price * day;
+            day += 1;
+
+            if top.pos > 0 {
+                heap.push(Item {
+                    price: values[top.shop][top.pos - 1] as i64,
+                    shop: top.shop,
+                    pos: top.pos - 1,
+                })
+            }
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2931() {
+        assert_eq!(
+            285,
+            Solution::max_spending(vec![vec![8, 5, 2], vec![6, 4, 1], vec![9, 7, 3]])
+        );
+    }
+}