Week Training: 215 Kth Largest Element in an Array

This is an exercise of the selection algorithm in the class this week just in time. In order to find the kth largest number, we first choose a random pivot, then put the numbers smaller and larger than it into 2 sequences. After that, if the size of the larger sequence is bigger than k, it does recursion in the larger sequence; if the size is smaller than rest length of the small sequence, do recursion in the small sequence with another k. The pivot finally returned is the answer.

class Solution {public:    int findKthLargest(vector<int>& nums, int k) {        srand(time(0));         int size = nums.size();        int n = rand()%size;        int pivot = nums[n];        vector<int> v1, v2;        for(int i=0;i<size;i++){            if(nums[i]>pivot)                v1.push_back(nums[i]);            else if(nums[i]<pivot)                v2.push_back(nums[i]);        }        if(k<=v1.size())            return findKthLargest(v1,k);        else if(k>(size-v2.size()))            return findKthLargest(v2,k-(size-v2.size()));        else            return pivot;    }};