Leetcode刷题指南C++(每日更新)_c++ leetcode刷题

1.两数之和

两数之和https://leetcode-cn.com/problems/two-sum/

//暴力枚举
class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        int n = nums.size();
        for (int i = 0; i < n; ++i) {
            for (int j = i + 1; j < n; ++j) {
                if (nums[i] + nums[j] == target) {
                    return {i, j};
                }
            }
        }
        return {};
    }
};

//哈希表
class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int, int> hashtable;
        for (int i = 0; i < nums.size(); ++i) {
            auto it = hashtable.find(target - nums[i]);
            if (it != hashtable.end()) {
                return {it->second, i};
            }
            hashtable[nums[i]] = i;
        }
        return {};
    }
};

2.合并两个有序链表

合并两个有序链表https://leetcode-cn.com/problems/merge-two-sorted-lists/

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {
        if(list1==nullptr){
            return list2;
        }else if(list2==nullptr){
            return list1;
        }else if(list1->val < list2->val){
            list1->next = mergeTwoLists(list1->next,list2);
            return list1;
        }else{
            list2->next = mergeTwoLists(list2->next,list1);
            return list2;
        }
        
    }
};

3.删除有序数组中的重复项

删除有序数组中的重复项https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array/

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int n = nums.size();
        if(n == 0){
            return 0;
        }
        int fast = 1, slow = 1;
        while(fast < n){
            if(nums[fast] !=nums[fast - 1]){
                nums[slow] = nums[fast];
                ++slow;
            }
            ++fast;
        }
        return slow;
 
    }
};