目录

1768 交替合并字符串 

1431 拥有最多糖果的孩子

605 种花问题

345 反转字符串中的元音字母

---

1768 交替合并字符串 

class Solution {
public:string mergeAlternately(string word1, string word2) {int n = max(word1.size(),word2.size());string res;for(int i = 0;i < n;i++){if(i < word1.size()){res += word1[i];}if(i < word2.size()){res += word2[i];}}return res;}
};

时间复杂度O(n+m)

空间复杂度O(1)

1431 拥有最多糖果的孩子

class Solution {
public:vector<bool> kidsWithCandies(vector<int>& candies, int extraCandies) {vector<bool>res(candies.size());int mx = -1;for(auto candy : candies){mx = max(mx,candy);}for(int i = 0;i < candies.size();i++){if(candies[i] + extraCandies >= mx){res[i] = true;}}return res;}
};

时间复杂度O(n)

空间复杂度O(1)

605 种花问题

数组前后都加上0，全部统一起来处理。 

class Solution {
public:bool canPlaceFlowers(vector<int>& flowerbed, int n) {int res = 0;flowerbed.insert(flowerbed.begin(),0);flowerbed.push_back(0);for(int i = 1;i < flowerbed.size() - 1;i++){if(flowerbed[i] == 0 && flowerbed[i - 1] == 0 && flowerbed[i + 1] == 0){res++;flowerbed[i] = 1;}}return res >= n;}
};

时间复杂度O(n)

空间复杂度O(1)

345 反转字符串中的元音字母

注意边界问题 

class Solution {
public:string reverseVowels(string s) {unordered_set<char>set{'a','e','i','o','u','A','E','I','O','U'};int l = 0;int r = s.size() - 1;while(r > l){while(r > l && !set.count(s[l]))l++;while(r > l && !set.count(s[r]))r--;if(r > l){s[l] ^= s[r];s[r] ^= s[l];s[l] ^= s[r];}l++;r--;}return s;}
};

时间复杂度O(n)

空间复杂度O(1)