16. 3Sum Closest

最新推荐文章于 2020-10-13 04:19:10 发布

sunnylinner

最新推荐文章于 2020-10-13 04:19:10 发布

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分类专栏： LeetCode 文章标签： java LeetCode

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本文介绍了一个算法问题：给定整数数组及目标值，寻找三个数使得其和最接近目标值，并返回这三个数的和。通过排序和双指针技术实现了高效求解。

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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).

算法思路见15题（就是上一题）~

<pre name="code" class="java">public class Solution {
	public int threeSumClosest(int[] nums, int target) {
		Arrays.sort(nums);
		int diff = Integer.MAX_VALUE, closest = 0;
		for (int k = 0; k < nums.length-2; k++) {
			if (k > 0 && (nums[k] == nums[k-1]))
				continue;
			for (int i = k+1, j = nums.length-1; i < j; ) {
				int sum = nums[k] + nums[i] + nums[j];
				if (sum == target) {
					return target;
				} else if (sum > target) {
					if (sum - target < diff) {
						diff = sum - target;
						closest = sum;
					}
					j--;
                    while((i < j) && (nums[j] == nums[j+1]))
						j--;//避免重复
				} else {
					if (target - sum < diff) {
						diff = target - sum;
						closest = sum;
					}
                    i++;
					while((i < j) && (nums[i] == nums[i-1]))
						i++;//避免重复
				}
			}
		}
		return closest;
	}
}