16. 3Sum Closest

Given an array of integers, find three integers in 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).

思路： Very close to 3Sum

    public int threeSumClosest(int[] nums, int target) {
        int min = Integer.MAX_VALUE;
        int result = 0;
        Arrays.sort(nums);

        for (int i=0;i<nums.length-2;i++){
            int left = i+1;
            int right = nums.length-1;
            while (left<right){
                int sum = nums[i]+nums[left]+nums[right];
                int diff = Math.abs(sum-target);

                if (diff==0){
                    return sum;
                }

                if (diff<min){
                    min = diff;
                    result = sum;
                }

                if (sum<target){
                    left++;
                }else{
                    right--;
                }
            }
        }

        return result;
    }
}]

C++ code

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        int minVal = INT_MAX;
        int res = 0;
        sort(nums.begin(),nums.end());

        for (int i=0; i<nums.size()-2; i++){
            int left = i+1;
            int right = nums.size()-1;
            while (left<right){
                int sum = nums[i]+nums[left]+nums[right];
                if (sum==target){
                    return sum;
                }

                int diff = abs(target-sum);
                if (diff<minVal){
                    res = sum;
                    minVal = diff;
                }

                if(sum<target){
                    left++;
                }else{
                    right--;
                }
            }
        }

        return res;
    }
};