# 【LeetCode】373. Find K Pairs with Smallest Sums 解题报告（Python）

# 题目描述：

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.

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

``````Example 1:
Given nums1 = [1,7,11], nums2 = [2,4,6],  k = 3

Return: [1,2],[1,4],[1,6]

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:
Given nums1 = [1,1,2], nums2 = [1,2,3],  k = 2

Return: [1,1],[1,1]

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:
Given nums1 = [1,2], nums2 = [3],  k = 3

Return: [1,3],[2,3]

All possible pairs are returned from the sequence:
[1,3],[2,3]
``````

# 解题方法

``````class Solution(object):
def kSmallestPairs(self, nums1, nums2, k):
"""
:type nums1: List[int]
:type nums2: List[int]
:type k: int
:rtype: List[List[int]]
"""
pairs = list(itertools.product(nums1, nums2))
return sorted(pairs, key = lambda x: sum(x))[:k]
``````

``````class Solution(object):
def kSmallestPairs(self, nums1, nums2, k):
"""
:type nums1: List[int]
:type nums2: List[int]
:type k: int
:rtype: List[List[int]]
"""
res = []
len1, len2 = len(nums1), len(nums2)
if not len1 or not len2: return res
heap = []
for x in range(len1):
heapq.heappush(heap, (nums1[x] + nums2[0], x, 0))
while len(res) < min(k, len1 * len2):
sum, i, j = heapq.heappop(heap)
res.append([nums1[i], nums2[j]])
if j + 1 < len2:
heapq.heappush(heap, (nums1[i] + nums2[j + 1], i, j + 1))
return res
``````

# 日期

2018 年 3 月 14 日 --霍金去世日