[leetcode 16] 3Sum Closest

最新推荐文章于 2026-01-08 21:36:59 发布

原创最新推荐文章于 2026-01-08 21:36:59 发布 · 208 阅读

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本文介绍了一个算法问题——寻找数组中三个整数的组合，使其和最接近给定的目标值，并提供了一种解决方案。通过排序和双指针技术实现了高效查找。

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：同3Sum，排序之后，夹逼

class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
        int res;
        if (num.size() < 3) {
            return res;
        }
        int min_gap = INT_MAX;  //记录最小的差值
        sort(num.begin(), num.end());
        auto last = num.end();
        for (auto i = num.begin(); i < last - 2; i++) {
            auto j = i + 1;
            auto k = last - 1;
            while (j < k) {
                int sum = *i + *j + *k;
                int gap = abs(sum - target);
                if (gap < min_gap) {
                    res = sum;
                    min_gap = gap;
                }
                if (sum > target) {
                    k--;
                } else {
                    j++;
                }
            }
        }
        return res;
    }
};