3Sum Closest

Posted 2023-01-20 IIcyZhao

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = -1 2 1 -4, and target = 1.

    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

class Solution 
public:
    int threeSumClosest(vector<int> &num, int target) 
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        sort(num.begin(), num.end());
        int sum = num[0] + num[1] + num[2];
        int result = sum;
        int min_gap = abs(sum - target);
        for (int i = 0; i < num.size() - 2; ++i) 
            int low = i + 1;
            int high = num.size() - 1;
            while (low < high) 
                sum = num[i] + num[low] + num[high];
                int gap = sum - target;
                if (gap > 0) 
                    min_gap = min_gap < gap ? min_gap : gap;
                    if (min_gap == gap) 
                        result = sum;
                    
                    --high;
                 else if (gap < 0) 
                    min_gap = min_gap < -gap ? min_gap : -gap;
                    if (min_gap == -gap) 
                        result = sum;
                    
                    ++low;
                 else 
                    return target;
                
            
        
        return result;
    
;