【LeetCode】 88. 合并两个有序数组

川长思鸟来 2021-06-10 20:38 479阅读 0赞

## <table>   <tbody>    <tr>     <td><font>题目</font></td>    </tr>   </tbody>  </table> ##

题目传送门：[传送门 （点击此处）][Link 1]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUxNTMxMjgzMg_size_16_color_FFFFFF_t_70]

## <table>   <tbody>    <tr>     <td><font>题解</font></td>    </tr>   </tbody>  </table> ##

这个实在是没绕过来，所以，只能靠官方题解了  
[https://leetcode-cn.com/problems/merge-sorted-array/solution/he-bing-liang-ge-you-xu-shu-zu-by-leetcode/][https_leetcode-cn.com_problems_merge-sorted-array_solution_he-bing-liang-ge-you-xu-shu-zu-by-leetcode]

其实三种解法的思路都很清晰，仔细看一看题解都可以掌握的，一点都不难，看完之后一定要手写实践一下！

### 方法一 : 合并后排序 ###

class Solution { 
      public void merge(int[] nums1, int m, int[] nums2, int n) { 
        System.arraycopy(nums2, 0, nums1, m, n);
        Arrays.sort(nums1);
      }
    }

方法二 : 双指针 / 从前往后

class Solution { 
      public void merge(int[] nums1, int m, int[] nums2, int n) { 
        // Make a copy of nums1.
        int [] nums1_copy = new int[m];
        System.arraycopy(nums1, 0, nums1_copy, 0, m);
    
        // Two get pointers for nums1_copy and nums2.
        int p1 = 0;
        int p2 = 0;
    
        // Set pointer for nums1
        int p = 0;
    
        // Compare elements from nums1_copy and nums2
        // and add the smallest one into nums1.
        while ((p1 < m) && (p2 < n))
          nums1[p++] = (nums1_copy[p1] < nums2[p2]) ? nums1_copy[p1++] : nums2[p2++];
    
        // if there are still elements to add
        if (p1 < m)
          System.arraycopy(nums1_copy, p1, nums1, p1 + p2, m + n - p1 - p2);
        if (p2 < n)
          System.arraycopy(nums2, p2, nums1, p1 + p2, m + n - p1 - p2);
      }
    }

方法三 : 双指针 / 从后往前

class Solution { 
      public void merge(int[] nums1, int m, int[] nums2, int n) { 
        // two get pointers for nums1 and nums2
        int p1 = m - 1;
        int p2 = n - 1;
        // set pointer for nums1
        int p = m + n - 1;
    
        // while there are still elements to compare
        while ((p1 >= 0) && (p2 >= 0))
          // compare two elements from nums1 and nums2 
          // and add the largest one in nums1 
          nums1[p--] = (nums1[p1] < nums2[p2]) ? nums2[p2--] : nums1[p1--];
    
        // add missing elements from nums2
        System.arraycopy(nums2, 0, nums1, 0, p2 + 1);
      }
    }

[Link 1]: https://leetcode-cn.com/problems/merge-sorted-array/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUxNTMxMjgzMg_size_16_color_FFFFFF_t_70]: /images/20210529/ca219f3129244db58189822da2a02e51.png
[https_leetcode-cn.com_problems_merge-sorted-array_solution_he-bing-liang-ge-you-xu-shu-zu-by-leetcode]: https://leetcode-cn.com/problems/merge-sorted-array/solution/he-bing-liang-ge-you-xu-shu-zu-by-leetcode/