【LeetCode 88】 Merge Sorted Array

題目描述

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

Note:

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

Example:

Input:
nums1 = [1,2,3,0,0,0], m = 3
nums2 = [2,5,6],       n = 3

Output: [1,2,2,3,5,6]

思路

從後往前，從大到小。

代碼

class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
        int tail = m + n - 1;
        int i = m-1, j = n-1;
        while(j >= 0) {
            nums1[tail--] = (i>=0 && nums1[i] > nums2[j]) ? nums1[i--] : nums2[j--];
        }
    }
};

2. 用vector的插入和pop_back

class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
        int pos1 = 0;
        int pos2 = 0;
        while(pos2 < n) {
            while(nums1[pos1] < nums2[pos2] && pos1 < pos2+m) pos1++;
            nums1.insert(nums1.begin()+pos1, nums2[pos2]);
            pos2++;
            nums1.pop_back();
        }
    }
};