LeetCode：合并两个有序链表与合并两个有序数组

一、合并两个有序链表

package cn.edu.neu.leetcode.linked_list;

/**
 * @author 32098
 */
public class MergeLinkedList {
    public static ListNode mergeTwoLists(ListNode a, ListNode b) {
        ListNode ans  = new ListNode();
        ListNode tmp = ans;
        while (a!=null && b!=null){
            if(a.val<b.val){
                tmp.val = a.val;
                a = a.next;
            }else{
                tmp.val = b.val;
                b = b.next;
            }
            tmp.next = new ListNode();
            tmp = tmp.next;
        }
        if(a==null && b!=null){
            tmp.val = b.val;
            tmp.next = b.next;
        }else if(a != null){
            tmp.val = a.val;
            tmp.next = a.next;
        }
        return ans;

        // 官方解法好一点，省内存
//        ListNode ans = new ListNode(-1);
//        ListNode tmp = ans;
//        while (a!=null && b!=null) {
//            if (a.val < b.val) {
//                tmp.next = a;
//                a = a.next;
//            } else {
//                tmp.next = b;
//                b = b.next;
//            }
//            tmp = tmp.next;
//        }
//        tmp.next = a==null?b:a;
//        return ans.next;
    }

    public static void main(String[] args) {
        int[] nums1 = new int[]{1, 2, 4};
        int[] nums2 = new int[]{1, 3, 4};
        ListNode nodeA = new ListNode(-1);
        ListNode nodeATmp = nodeA;
        ListNode nodeB = new ListNode(-1);
        ListNode nodeBTmp = nodeB;
        for (int i : nums1) {
            nodeATmp.next = new ListNode(i);
            nodeATmp = nodeATmp.next;
        }
        for (int i : nums2) {
            nodeBTmp.next = new ListNode(i);
            nodeBTmp = nodeBTmp.next;
        }
        mergeTwoLists(nodeA.next, nodeB.next);
    }
}

二、合并两个有序数组

package cn.edu.neu.leetcode.normal;

/**
 * @author 32098
 */
public class MergeSortedArray {
    // 相比官方解法代码过长
    public static void merge(int[] nums1, int m, int[] nums2, int n) {
        int ind = m+n-1;
        int i = m-1;
        int j = n-1;
        while (ind>=0){
            if(i<0 || j<0){
                break;
            }
            if(nums1[i]>nums2[j]){
                nums1[ind] = nums1[i];
                i--;
            }else {
                nums1[ind] = nums2[j];
                j--;
            }
            ind--;
        }
        if(i>=0){
            for(int k=i; k>=0; k--){
                nums1[ind] = nums1[k];
                ind--;
            }
        }
        if(j>=0){
            for(int k=j; k>=0; k--){
                nums1[ind] = nums2[k];
                ind--;
            }
        }
    }

    public static void main(String[] args) {
        merge(new int[]{1, 2, 3, 0, 0, 0}, 3, new int[]{2, 5, 6}, 3);

    }
}