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  • LeetCode

    题目:

    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).

    思路:

    和3sum一样,排序之后,先确定第一个元素,然后对余下元素进行两边夹。

    package sum;
    
    import java.util.Arrays;
    
    public class ThreeSumClosest {
    
        public int threeSumClosest(int[] nums, int target) {
            int len = nums.length;
            Arrays.sort(nums);
            
            int delta = nums[0] + nums[1] + nums[2] - target;
            for (int i = 0; i < len - 2;) {
                int l = i + 1;
                int r = len - 1;
                while (l < r) {
                    int tmp = nums[i] + nums[l] + nums[r] - target;
                    if (Math.abs(tmp) < Math.abs(delta))
                        delta = tmp;
                    if (tmp == 0)
                        return target;
                    if (tmp < 0)
                        ++l;
                    else
                        --r;
                }
                
                do { ++i; } while (i < len && nums[i] == nums[i - 1]);
            }
            
            return target + delta;
        }
        
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            int[] nums = { -1, 2, 1, -4 };
            int target = 1;
            ThreeSumClosest t = new ThreeSumClosest();
            System.out.println(t.threeSumClosest(nums, target));
        }
    
    }
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  • 原文地址:https://www.cnblogs.com/null00/p/5025899.html
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