20240722 Finished

src/problem/mod.rs

@@ -181,3 +181,4 @@ mod p34_find_first_and_last_position_of_element_in_sorted_array;
 mod p153_find_minimum_in_rotated_sorted_array;
 mod p215_kth_largest_element_in_an_array;
 mod p502_ipo;
+mod p373_find_k_pairs_with_smallest_sums;

src/problem/p373_find_k_pairs_with_smallest_sums.rs

@@ -0,0 +1,86 @@
+/**
+ * [373] Find K Pairs with Smallest Sums
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+use std::cmp::Ordering;
+
+#[derive(Eq, PartialEq)]
+struct Pair<'a> {
+    nums1: &'a Vec<i32>,
+    nums2: &'a Vec<i32>,
+    x: usize,
+    y: usize,
+}
+
+impl Pair<'_> {
+    fn new<'a>(nums1: &'a Vec<i32>, nums2: &'a Vec<i32>, x: usize, y: usize) -> Pair<'a> {
+        Pair {
+            nums1,
+            nums2,
+            x,
+            y,
+        }
+    }
+}
+
+impl Ord for Pair<'_> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        (other.nums1[other.x] + other.nums2[other.y]).cmp(
+            &(self.nums1[self.x] + self.nums2[self.y]))
+    }
+}
+
+impl PartialOrd for Pair<'_> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Solution {
+    pub fn k_smallest_pairs(nums1: Vec<i32>, nums2: Vec<i32>, k: i32) -> Vec<Vec<i32>> {
+        use std::collections::BinaryHeap;
+
+        let (m, n) = (nums1.len(), nums2.len());
+        let k = k as usize;
+
+        let mut heap = BinaryHeap::new();
+
+        for i in 0..m.min(k) {
+            heap.push(Pair::new(&nums1, &nums2, i, 0));
+        }
+
+        let mut count = 0;
+        let mut result = Vec::with_capacity(k);
+
+        while count < k && !heap.is_empty() {
+            let pair = heap.pop().unwrap();
+            let (x, y) = (pair.x, pair.y);
+            result.push((nums1[x], nums2[y]));
+
+            if y + 1 < n {
+                heap.push(Pair::new(&nums1, &nums2, x, y + 1));
+            }
+
+            count += 1;
+        }
+
+
+        result.iter().map(|(x, y)| vec![*x, *y]).collect()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_373() {
+        assert_eq!(vec![vec![1, 2], vec![1, 4], vec![1, 6]],
+                   Solution::k_smallest_pairs(vec![1, 7, 11], vec![2, 4, 6], 3));
+    }
+}