45 lines
1.0 KiB
Rust
45 lines
1.0 KiB
Rust
pub fn kth_largest(mut nums: Vec<i32>, k: i32) -> Option<i32> {
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if nums.is_empty() || k >= nums.len() as i32 { return None; }
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let end = nums.len() - 1;
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let k = k as usize;
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// 分区点
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let mut pivot = partition(&mut nums, 0, end);
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while pivot + 1 != k {
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if k > pivot + 1 {
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pivot = partition(&mut nums, pivot + 1, end);
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} else {
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pivot = partition(&mut nums, 0, pivot - 1);
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}
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}
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Some(nums[pivot])
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}
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fn partition(nums: &mut Vec<i32>, start: usize, end: usize) -> usize {
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let pivot = nums[end];
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let mut i = start;
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for j in start..end {
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if nums[j] >= pivot { // if nums[j] <= pivot then swap, search kth smallest
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swap(nums, i, j);
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i += 1;
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}
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}
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swap(nums, i, end);
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i
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}
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fn swap(nums: &mut Vec<i32>, i: usize, j: usize) {
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if i == j { return; }
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let tmp = nums[i];
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nums[i] = nums[j];
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nums[j] = tmp;
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}
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fn main() {
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let nums = vec![8, 10, 2, 3, 6,1, 5];
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println!("{:?}", kth_largest(nums, 3));
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}
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