LintCode "Median"

Partial Sort.

class Solution {
public:
    /**
     * @param nums: A list of integers.
     * @return: An integer denotes the middle number of the array.
     */
    int partition(vector<int> &nums, int s, int e)
    {
        if (s > e) return -1;

        int pivot = nums[s];
        swap(nums[s], nums[e]);
        int i = s, j = s;
        while(j < e)
        {
            if(nums[j] <= pivot)
            {
                swap(nums[i ++], nums[j]);
            }
            j ++;
        }
        swap(nums[i], nums[e]);

        return i;   
    }
    int findKth(vector<int> &nums, int inx, int s, int e)
    {
        int pi = partition(nums, s, e);
        if(pi == inx) return nums[inx];
        if (pi < inx) return findKth(nums, inx, pi+1, e);
        return findKth(nums, inx, s, pi-1);
    }
    int median(vector<int> &nums) {
        size_t len = nums.size();
        int mid = len/2 - (len%2?0:1);
        return findKth(nums, mid, 0, len - 1);
    }
};