leetcode两题

class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
      int res=0;
        sort(nums.begin(),nums.end());
        for (int i=0;i<nums.size();i=i+2)
        {
            res+=nums[i];
        }
        return res;
    }
};

Example 1:

Input: [1,4,3,2]

Output: 4
Explanation: n is 2, and the maximum sum of pairs is 4 = min(1, 2) + min(3, 4).

Note:

1. n is a positive integer, which is in the range of [1, 10000].
2. All the integers in the array will be in the range of [-10000, 10000].

class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
      int res=0;
        sort(nums.begin(),nums.end());
        for (int i=0;i<nums.size();i=i+2)
        {
            res+=nums[i];
        }
        return res;
    }
};

2

Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

class Solution {
public:
    string reverseString(string s) {
        int lenth=s.length();
        for(int i=0;i<lenth/2;i++)
        {
            char a=s[i];
            s[i]=s[lenth-i-1];
            s[lenth-i-1]=a;
        }
        return s;  
        
    }
};

注：字符串s长度用s.length();

       容器的大小用nums.size()