29 lines
723 B
C++
29 lines
723 B
C++
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#include<bits/stdc++.h>
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using namespace std;
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const int N = 5000010;
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int a[N];
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void quick_sort(int q[], int l, int r, int k) {
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if (l >= r)return;
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int i = l - 1, j = r + 1, x = q[(l + r) >> 1];
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while (i < j) {
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do i++; while (q[i] < x);
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do j--; while (q[j] > x);
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if (i < j)swap(q[i], q[j]);
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}
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int sl = j - l + 1;
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if (k <= sl) quick_sort(q, l, j, k);//左半部分搜索
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else quick_sort(q, j + 1, r, k - sl);//右半部分搜索
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}
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int main() {
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//优化输入
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ios::sync_with_stdio(false);
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int n, k;
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cin >> n >> k;
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for (int i = 0; i < n; i++)cin >> a[i];
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quick_sort(a, 0, n - 1, k);
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printf("%d", a[k]);
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return 0;
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}
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