题解 | #最小的K个数#

#include <vector>
class Solution {
public:
    int partition(vector<int>& vec, int left, int right) {
        int pivot = vec[left];
        int i = left + 1;
        for (int j = left + 1; j <= right; j++) {
            if (vec[j] < pivot) {
                swap(vec[i++], vec[j]);
            }
        }
        swap(vec[i - 1], vec[left]);
        return i - 1;
    }

    vector<int> GetLeastNumbers_Solution(vector<int>& input, int k) {
        vector<int> res;
        if (k == 0 || k > input.size()) return res;

        int left = 0, right = input.size() - 1;
        while (left <= right) {
            int index = partition(input, left, right);
            if (index == k - 1) {
                return vector<int>(input.begin(), input.begin() + k);
            } else if (index < k - 1) {
                left = index + 1;
            } else {
                right = index - 1;
            }
        }
        return res;
    }
};