HDU 1425 sort（堆排序/快排/最大堆/最小堆）

传送门

Description

给你n个整数，请按从大到小的顺序输出其中前m大的数。

Input

每组测试数据有两行，第一行有两个数n,m(0<n,m<1000000)，第二行包含n个各不相同，且都处于区间[-500000,500000]的整数。

Output

对每组测试数据按从大到小的顺序输出前m大的数。

Sample Input

5 3 
3 -35 92 213 -644

Sample Output

213 92 3

1、使用内建sort函数

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#include<iostream> #include<algorithm> #include<cstdio> using namespace std; int ans[1000001]; int main() {     int n,m;     while (scanf("%d%d",&n,&m) != EOF)     {         for (int i = 0;i < n;i++)         {             scanf("%d",&ans[i]);         }         sort(ans,ans + n);         printf("%d",ans[n - 1]);         for(int i = n - 2;m > 1;m--,i--)         {             printf(" %d",ans[i]);         }         printf("\n");     }     return 0; }

2、使用内建优先队列

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#include<iostream> #include<queue> #include<cstdio> using namespace std;   int main() {     int N,M;     while (~scanf("%d%d",&N,&M))     {         priority_queue<int>que;         bool first = true;         int tmp;         while (N--)         {             scanf("%d",&tmp);             que.push(tmp);         }         while (M--)         {             first?printf("%d",que.top()):printf(" %d",que.top());             que.pop();             first = false;         }         printf("\n");     }     return 0; }

3、使用内部堆函数

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#include <cstdio> #include <algorithm> using namespace std;   static int a[1000000];   int main() {     int i,n,m;     while(EOF != scanf("%d %d",&n,&m))     {         for(i=0;i<n;i++)             scanf("%d",&a[i]);         make_heap(a,a+n);         printf("%d",a[0]);         for(i=1;i<m;i++)         {             pop_heap(a,a+n-i+1);             printf(" %d",a[0]);         }         printf("\n");     }     return 0; }

4、手写最大堆

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#include<stdio.h> #include<string.h> const int maxn = 1000005; int heap[maxn],sz = 0;   void push(int x) {     int i = sz++;     while (i > 0)     {         int p = (i - 1)/2;         if (heap[p] >= x)    break;         heap[i] = heap[p];         i = p;     }     heap[i] = x; }   int pop() {     int ret = heap[0];     int x = heap[--sz];     int i = 0;     while (i*2+1<sz)     {         int a = i*2+1,b = i*2+2;         if (b < sz && heap[b]>heap[a])    a = b;         if (heap[a] <= x)    break;         heap[i] = heap[a];         i = a;     }     heap[i] = x;     return ret; }   int main() {     int n,m,tmp;     while (~scanf("%d%d",&n,&m))     {         sz = 0;         memset(heap,0,sizeof(heap));         for (int i = 0;i < n;i++)    scanf("%d",&tmp),push(tmp);         for (int i = 1;i < m;i++)    printf("%d ",pop());         printf("%d\n",pop());     }     return 0; }

5、手写堆排序（从大到小）

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#include<bits/stdc++.h> using namespace std; #define LeftChild(i) (2*(i)+1) const int maxn = 1000005; int a[maxn];   void PercDown(int a[],int i,int N) {     int Child;     int tmp;     for (tmp = a[i];LeftChild(i) <N;i = Child)     {         Child = LeftChild(i);         if (Child != N - 1 && a[Child+1] < a[Child])             Child++;         if (tmp > a[Child])             a[i] = a[Child];         else             break;     }     a[i] = tmp; }   void Heapsort(int a[],int N) {     int i;     for (i = N/2;i >= 0;i--)         PercDown(a,i,N);     for (i = N-1;i > 0;i--)     {         swap(a[0],a[i]);         PercDown(a,0,i);     } }   int main() {     int n,m;     while (~scanf("%d%d",&n,&m))     {         for (int i = 0;i < n;i++)    scanf("%d",&a[i]);         Heapsort(a,n);         printf("%d",a[0]);         for (int i = 1;i < m;i++)    printf(" %d",a[i]);         printf("\n");     }     return 0; }

6、手写堆排序（从小到大）

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#include<cstdio> #include<algorithm> using namespace std; #define LeftChild(i) (2*(i)+1) const int maxn = 1000005; int a[maxn];   void PercDown(int a[],int i,int N) {     int Child;     int tmp;     for (tmp = a[i];LeftChild(i) <N;i = Child)     {         Child = LeftChild(i);         if (Child != N - 1 && a[Child+1] > a[Child])             Child++;         if (tmp < a[Child])             a[i] = a[Child];         else             break;     }     a[i] = tmp; }   void Heapsort(int a[],int N) {     int i;     for (i = N/2;i >= 0;i--)         PercDown(a,i,N);     for (i = N-1;i > 0;i--)     {         swap(a[0],a[i]);         PercDown(a,0,i);     } }   int main() {     int n,m;     while (~scanf("%d%d",&n,&m))     {         for (int i = 0;i < n;i++)    scanf("%d",&a[i]);         Heapsort(a,n);         printf("%d",a[n-1]);         for (int i = n-2;i > n-1 - m;i--)    printf(" %d",a[i]);         printf("\n");     }     return 0; }

7、手写快速排序（从大到小）

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#include<bits/stdc++.h> using namespace std; #define Cutoff (3) const int maxn = 1000005; int a[maxn];   void InsertionSort(int a[],int N) {     int i,j,tmp;     for (i = N - 2;i >= 0;i--)     {         tmp = a[i];         for (j = i;j < N - 1 && a[j + 1] > tmp;j++)             a[j] = a[j + 1];         a[j] = tmp;     } }   int median3(int a[],int left,int right) {     int center = (left + right) / 2;     if (a[left] < a[center])         swap(a[left],a[center]);     if (a[left] < a[right])         swap(a[left],a[right]);     if (a[center] < a[right])         swap(a[center],a[right]);     swap(a[center],a[left + 1]);     return a[left + 1]; }   void qsort(int a[],int left,int right) {     int i,j,pivot;     if (left + Cutoff <= right)     {         pivot = median3(a,left,right);         i = left + 1;j = right;         for (;;)         {             while (a[++i] > pivot){}             while (a[--j] < pivot){}             if (i < j)    swap(a[i],a[j]);             else    break;         }         swap(a[j],a[left + 1]);         qsort(a,left,j - 1);         qsort(a,j + 1,right);     }     else    InsertionSort(a + left,right - left + 1); }   int main() {     int n,m;     while (~scanf("%d%d",&n,&m))     {         for (int i = 0;i < n;i++)    scanf("%d",&a[i]);         qsort(a,0,n - 1);         printf("%d",a[0]);         for (int i = 1;i < m;i++)    printf(" %d",a[i]);         printf("\n");     }     return 0; }

8、手写快速排序（从小到大）

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#include<bits/stdc++.h> using namespace std; const int Cutoff = 10; const int maxn = 1000005; int a[maxn]; void InsertionSort(int a[],int N) {     int i,j,tmp;     for (i = 1;i < N;i++)     {         tmp = a[i];         for (j = i;j > 0 && a[j - 1] > tmp;j--)             a[j] = a[j - 1];         a[j] = tmp;     } } int median3(int a[],int left,int right) {     int center = (left + right) / 2;     if (a[left] > a[center])         swap(a[left],a[center]);     if (a[left] > a[right])         swap(a[left],a[right]);     if (a[center] > a[right])         swap(a[center],a[right]);     swap(a[center],a[right-1]);     return a[right-1]; } void qsort(int a[],int left,int right) {     int i,j,pivot;     if (left + Cutoff <= right)     {         pivot = median3(a,left,right);         i = left;j = right-1;         for (;;)         {             while (a[++i] < pivot){}             while (a[--j] > pivot){}             if (i < j)    swap(a[i],a[j]);             else    break;         }         swap(a[i],a[right-1]);         qsort(a,left,i - 1);         qsort(a,i + 1,right);     }     else    InsertionSort(a + left,right - left + 1); } int main() {     int n,m;     while (~scanf("%d%d",&n,&m))     {         for (int i = 0;i < n;i++)    scanf("%d",&a[i]);         qsort(a,0,n - 1);         printf("%d",a[n - 1]);         for (int i = n - 2;i > n - m - 1;i--)    printf(" %d",a[i]);         printf("\n");     }     return 0; }