// method 2 use extra space to get optimal pivot selection
int findKthLargest(vector<int>& nums, int k) {
int n = nums.size();
if (n==1) return nums[0];
int big = nums[0], small = big;
vector<int> left;
vector<int> right;
for (int i = 1; i < n; i++) {
if (nums[i] > big)
big = nums[i];
if (nums[i] < small)
small = nums[i];
}
const double mid = (big + small) / 2.0; // use the medium as partition pivot
for (int i = 0; i < n; i++) {
if (nums[i] <= mid)
left.push_back(nums[i]);
else
right.push_back(nums[i]);
}
if (left.size() == n) return nums[0]; // all the elements are equal.
if (left.size() >= n-k+1)
return findKthLargest(left, k-right.size());
else
return findKthLargest(right, k);
}
int findKthLargest(vector<int>& nums, int k) {
vector<int>lt_pivot,gt_pivot;
int pivot = nums[random(nums.size())];
for(int num:nums)
{
if(num>pivot) gt_pivot.push_back(num);
else if(num<pivot) lt_pivot.push_back(num);
}
if(k<=gt_pivot.size())
return findKthLargest(gt_pivot,k);
else if(k>nums.size()-lt_pivot.size())
return findKthLargest(lt_pivot,k-(nums.size()-lt_pivot.size()));
else
return pivot;
}
int main () {
//int arr[]={3,2,3,1,2,4,5,5,6};
int arr[]={7,6,5,4,3,2,1};
int k = 2;
printf ("\n%d largest is %d\n", k, findKthLargest(arr, sizeof(arr)/sizeof(arr[0]), k));
return 0;
}
int main(){
int arr[] = {3,2,1,5,6,4};
vector<int> nums(arr, arr + sizeof(arr) / sizeof(int));
for(int i=1; i<=nums.size(); i ++){
cout<<findKthLargest(nums, i)<<endl;
}
return 0;
}
int findKthLargest(int* nums, int numsSize, int k) {
if (numsSize == 0)
return -1;
if (numsSize == 1)
return nums[0];
int item = nums[numsSize-1];
int greaters = 0, equals = 0;
for (int pos = 0; pos < numsSize-1; pos++){
if (item < nums[pos])
greaters++;
else if (item == nums[pos])
equals++;
}
if (greaters > (k - 1))
return (findKthLargest(nums, numsSize-1, k));
if (greaters == (k - 1))
return item;
if (greaters + equals >= (k - 1))
return item;
return (findKthLargest(nums, numsSize-1, k-1));
}
int findKthLargest(vector<int>& nums, int k) {
int length = nums.size();
if (length == 1) {
return nums[0];
}
vector<int> left;
vector<int> right;
for (int index=1; index<length; index++) {
if (nums[index] > nums[0]) {
right.push_back(nums[index]);
}else{
left.push_back(nums[index]);
}
}
length = right.size();
if (length >=k) {
return findKthLargest(right, k);
}else if(length == k-1){
return nums[0];
}else{
return findKthLargest(left, k-length-1);
}
}
int Mymain()
{
std::vector<int> nums;
GenerateRandomArray(nums, 10001);
auto nums_s = nums;
int k = 1539;
int myk = 0, stdk = 2;
{TIC
//startQuickSort(nums, 0, nums.size() - 1);
myk = findKthLargest(nums, k);
TOC}
{TIC
std::sort(nums_s.begin(), nums_s.end());
stdk = nums_s[nums.size() - k];
TOC}
cout << "Check increase : " << std::boolalpha << CheckSorted(nums, nIncrease) << std::noboolalpha << endl;
cout << "Check K Largest : " << std::boolalpha << (myk == stdk) << std::noboolalpha << endl;
return 0;
}
int main() {
int a[] = {5,2,4,1,3,6,0};
vector<int> b = arrayToVector(a, 7);
cout<<findKthLargest(b, 4)<<endl;
return 0;
}
