threeSumClosest.cpp

#include <vector>
#include <math.h>
#include <algorithm>

using namespace std;

class Solution
{
public:
    int threeSumClosest(vector<int> &nums, int target)
    {
        //双指针
        sort(nums.begin(),nums.end());

        int clothestNum1 = 99999;

        for (int i = 0; i < nums.size() - 2; i++)
        {
            //外面只定义指针，运算更新要在指针运算外
            int left = i + 1;
            int right = nums.size() - 1;

            while(left < right)
            {
                int sum = nums[left] + nums[right] + nums[i];
                int gap = abs(sum - target);
                
                if(gap < abs(clothestNum1 - target))
                {
                    clothestNum1 = sum;
                }
                if (clothestNum1 == target)
                {
                    return target;
                }
                //移动指针相关逻辑
                if(sum < target)
                {
                    left++;
                }
                else
                {
                    right--;
                }
            }
        }

        return clothestNum1;
    }
};