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LeetCode OJ 215. Kth Largest Element in an Array

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example,
Given [3,2,1,5,6,4] and k = 2, return 5.

Note: 
You may assume k is always valid, 1 ≤ k ≤ array‘s length.

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

 

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解答

用堆排序就好了……不过这个堆是从0开始的,还有点不适应orz

int findKthLargest(int* nums, int numsSize, int k) {
    int i, j, tmp, largest;
    
    for(i = (numsSize - 2) / 2; i >= 0; i--){
        while(i * 2 + 1 < numsSize){
            if(i * 2 + 2 < numsSize&&nums[i * 2 + 1] < nums[i * 2 + 2]){
                largest = i * 2 + 2;
            }
            else{
                largest = i * 2 + 1;
            }
            if(nums[i] < nums[largest]){
                tmp = nums[i];
                nums[i] = nums[largest];
                nums[largest] = tmp;
                i = largest;
            }
            else{
                break;
            }
        }
    }
    for(j = 0; j < k - 1; j++){
        nums[0] = nums[numsSize - 1];
        numsSize--;
        i = 0;
        while(i * 2 + 1 < numsSize){
            if(i * 2 + 2 < numsSize&&nums[i * 2 + 1] < nums[i * 2 + 2]){
                largest = i * 2 + 2;
            }
            else{
                largest = i * 2 + 1;
            }
            if(nums[i] < nums[largest]){
                tmp = nums[i];
                nums[i] = nums[largest];
                nums[largest] = tmp;
                i = largest;
            }
            else{
                break;
            }
        }
    }
    return nums[0];
}

 

LeetCode OJ 215. Kth Largest Element in an Array