16.3SumClosest.cpp

#include<bits/stdc++.h>
using namespace std;

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        
        sort(nums.begin(), nums.end());
        int n = nums.size(), ans = nums[0] + nums[1] + nums[2];
        for (int i = 0; i < n-2; ++i) {
            int l = i + 1, r = n - 1;
            while (l < r) {
                int sum3 = nums[i] + nums[l] + nums[r];
                if (abs(ans - target) > abs(sum3 - target)) // Update better ans
                    ans = sum3;
                if (sum3 == target) break;
                if (sum3 > target)
                    --r; // Sum3 is greater than the target, to minimize the difference, we have to decrease our sum3
                else
                    ++l; // Sum3 is lesser than the target, to minimize the difference, we have to increase our sum3
            }
        }
        return ans;
        
    }
};