LeetCode|Merge Two Sorted Lists/Merge Sorted Array

Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode head(-1), *l = &head;
while(l1 && l2){
if(l1->val <= l2->val){
l->next = l1;
l = l->next;
l1 = l1->next;
} else{
l->next = l2;
l = l2;
l2 = l2->next;
}
} if(l1){
l->next = l1;
} else {
l->next = l2;
} return head.next;
}
};

head方便统一情况，同时便于最终的返回。

Merge Sorted Array

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

Note:

You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. The number of elements initialized in nums1 and nums2 are m and n respectively.

思路：假设是递增的序列，那么从后往前插数可以减少数组的移动。

class Solution {
public:
void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
int end = m-- + n-- - 1;
while(m >= 0 && n >= 0){
if(nums1[m] >= nums2
){
nums1[end--] = nums1[m--];
} else{
nums1[end--] = nums2[n--];
}
} while(n >= 0){
nums1[end--] = nums2[n--];
} return;
}
};