# [LeetCode] 373. Find K Pairs with Smallest Sums 找和最小的K对数字

You are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k.

Define a pair (u, v) which consists of one element from the first array and one element from the second array.

Return the k pairs (u1, v1), (u2, v2), ..., (uk, vk) with the smallest sums.

Example 1:

Input: nums1 = [1,7,11], nums2 = [2,4,6], k = 3
Output: [[1,2],[1,4],[1,6]]
Explanation: The first 3 pairs are returned from the sequence: [1,2],[1,4],[1,6],[7,2],[7,4],[11,2],[7,6],[11,4],[11,6]


Example 2:

Input: nums1 = [1,1,2], nums2 = [1,2,3], k = 2
Output: [[1,1],[1,1]]
Explanation: The first 2 pairs are returned from the sequence: [1,1],[1,1],[1,2],[2,1],[1,2],[2,2],[1,3],[1,3],[2,3]


Example 3:

Input: nums1 = [1,2], nums2 = [3], k = 3
Output: [[1,3],[2,3]]
Explanation: All possible pairs are returned from the sequence: [1,3],[2,3]


Constraints:

• 1 <= nums1.length, nums2.length <= 104
• -109 <= nums1[i], nums2[i] <= 109
• nums1 and nums2 both are sorted in ascending order.
• 1 <= k <= 1000

Credits:
Special thanks to @elmirap and @StefanPochmann for adding this problem and creating all test cases.

// Time Limit Exceeded
class Solution {
public:
vector<vector<int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k) {
vector<vector<int>> res;
for (int i = 0; i < min((int)nums1.size(), k); ++i) {
for (int j = 0; j < min((int)nums2.size(), k); ++j) {
res.push_back({nums1[i], nums2[j]});
}
}
sort(res.begin(), res.end(), [](vector<int> &a, vector<int> &b){return a[0] + a[1] < b[0] + b[1];});
if (res.size() > k) res.erase(res.begin() + k, res.end());
return res;
}
};

class Solution {
public:
vector<vector<int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k) {
vector<vector<int>> res;
priority_queue<pair<int, vector<int>>> pq;
for (int num1 : nums1) {
for (int num2 : nums2) {
int sum = num1 + num2;
if (pq.size() < k) {
pq.push({sum, {num1, num2}});
} else if (sum < pq.top().first) {
pq.pop();
pq.push({sum, {num1, num2}});
} else {
break;
}
}
}
while (!pq.empty()) {
res.push_back(pq.top().second);
pq.pop();
}
return res;
}
};

Github 同步地址：

https://github.com/grandyang/leetcode/issues/373

https://leetcode.com/problems/find-k-pairs-with-smallest-sums/

https://leetcode.com/problems/find-k-pairs-with-smallest-sums/solutions/4058698/c-priority-queue-k-max-heap-method-most-efficient/

LeetCode All in One 题目讲解汇总(持续更新中...)

posted @ 2016-07-08 13:39  Grandyang  阅读(17532)  评论(2编辑  收藏  举报