leetcode solution 16 3Sum closest
z
 2018-03-02 00:34:20  

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.

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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).

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class Solution {
    public int threeSumClosest(int[] nums, int target) {
        Arrays.sort(nums);
        int ans = nums[0] +nums[1] + nums[nums.length-1];
        
        for(int i = 0; i<nums.length-2; i++){
            int first = i+1;
            int last = nums.length - 1;
            while(first < last){
                if(Math.abs(nums[first] + nums[last] + nums[i] - target) < Math.abs(target- ans)){
                    ans = nums[first] + nums[last] + nums[i];
                }
                if(nums[first] + nums[last] + nums[i] > target){
                    last --;
                }
                else{
                    first ++;
                }
                
            }
        }
        return ans;
        
    }
}
  • using three pointer i first last , each time compare sum(i, first, last). if sum > target, moving first to the next, otherwise, moving last to the left next one.
  • Each time, we keep the closest sum to ans