LeetCode 16. 3Sum Closest

三数之和最接近目标

最新推荐文章于 2021-08-11 08:50:42 发布

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本文介绍了一种寻找数组中三个整数之和最接近给定目标值的有效算法。通过先排序后使用双指针技术，实现了快速查找最优解的方法。

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).

先排序再二分，情况比3sum要简单！

code in Java:

  public int threeSumClosest(int[] nums, int target) {
        int length = nums.length;
        int min = Integer.MAX_VALUE;
        int left, right, comp, result = 0;
 
        if (length < 3)
            return 0;
        Arrays.sort(nums);
 
        for (int i = 0; i < length - 2; i++) {
            left = i + 1;
            right = length - 1;
            while (left < right) {
                comp = nums[i] + nums[left] + nums[right];
                if (Math.abs(comp - target) < min){
                    min = Math.abs(comp - target);
                    result = comp;
                }
                if (comp > target)
                    right--;
                else if (comp < target)
                    left++;
                else
                    return target;
            }
        }
        return result;
    }