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]
A:
自己看下面的解法有什么问题,啊哈哈public class Solution { public List<int[]> kSmallestPairs(int[] nums1, int[] nums2, int k) { List<int[]> res = new LinkedList(); int i = 0,j=0, m = nums1.length, n = nums2.length; k = Math.min(k,m*n); while(k-- >= 0){ int[] tmp = {nums1[i],nums2[j]}; res.add(tmp); if(i==m-1){ j++; }else if(j==n-1){ i++; }else{ if(nums1[i+1]+nums2[j] < nums1[i]+nums2[j+1]) i++; else j++; } } return res; } }
-------Use priority heap----------
public class Solution { public List<int[]> kSmallestPairs(int[] nums1, int[] nums2, int k) { List<int[]> res = new LinkedList(); int m = nums1.length, n = nums2.length; if(m==0 || n == 0 || k <=0) return res; int[] index = new int[m];// for nums1 PriorityQueue<int[]> minHeap = new PriorityQueue<>(m, (A, B) -> A[1] + A[2] - B[1] - B[2]); for(int i = 0;i<m;i++) // put the initial values minHeap.offer(new int[]{i, nums1[i], nums2[0]}); while( !minHeap.isEmpty() && k-- > 0){ int[] top = minHeap.poll(); res.add(new int[]{top[1], top[2]}); int t = top[0]; // index of which element of nums1 is used. if(index[t] +1 < n)//if next move on nums2 is also valid, minHeap.add( new int[]{t, nums1[t], nums2[++index[t]]} ); } return res; } }
Error:
没有考虑Example 3的情况,没有读完题意呀,😌Java Lambda to write a comparator
clearly to understand how make a minHeap and maxHeap in the Compare method()
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