#include <iostream> #include <algorithm> #include <queue> using namespace std; int main(){ int n; while(scanf("%d",&n)!=EOF){ priority_queue<int, vector<int>, greater<int>> Q; int tmp; for(int i=0;i<n;i++){ scanf("%d", &tmp); Q.push(tmp); } int k; scanf("%d", &k); tmp = Q.top(); Q.pop(); for(int i=2;i<=k;i++){ while(tmp==Q.top()) Q.pop(); tmp = Q.top(); Q.pop(); } printf("%d\n", tmp); } }
#include<bits/stdc++.h> int main(){ int n; while(scanf("%d",&n)!=EOF){ int a[10000]={0},k=0; for(int i=0;i<n;i++){ scanf("%d",&k); a[k]++; } scanf("%d",&k); int s=0; for(int i=0;i<10000;i++){ if(a[i]>0) s++; if(s==k){ s=i; break; } } printf("%d\n",s); } }//hash法,也可用堆
import java.util.Arrays; import java.util.HashSet; import java.util.Scanner; import java.util.Set; public class Main { public static Set<Integer> set; public static void main(String[] args) { Scanner scan = new Scanner(System.in); int n = scan.nextInt(); set = new HashSet<>(); for(int i = 0; i < n; i++) set.add(scan.nextInt()); Object[] converted = set.toArray(); Arrays.sort(converted); System.out.println(converted[scan.nextInt() - 1]); scan.close(); } }
map的键会自动按序排列。
#include <iostream>
#include <map>
using namespace std;
int main()
{
int n,i,k,tmp;
while(cin>>n)
{
map<int,int> mmap;
for(i=0;i<n;++i)
{
cin>>tmp;
mmap[tmp]=1;
}
cin>>k;
auto it=mmap.begin();
for(;it!=mmap.end()&&k!=1;++it,--k){}
cout << it->first << endl;
}
return 0;
}
运行时间:44ms
占用内存:10932k
思路、注释,在代码里了。
import java.util.Arrays;
import java.util.Scanner;
/**
* @author Allen_Hua
* @create_time 创建时间:May 11, 2018 9:24:25 PM 类说明
*/
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
while (scan.hasNext()) {
int n = scan.nextInt();
int[] arr = new int[n];
for (int i = 0; i < arr.length; i++) {
arr[i] = scan.nextInt();
}
int k = scan.nextInt();// 第k小的数
// 从小到大排了序
Arrays.sort(arr);
// 遇到一种新的元素就加一 默认arr[0]是一种元素 temp初始化值为1
int temp = 1;
for (int i = 1; i < arr.length; i++) {
// 如果该数和前面一个数一样 则continue
// 不会执行循环体内该句下面的代码
if (arr[i] == arr[i - 1]) {
continue;
} else {// 如果该数和前面一个数不一样 则遇到了新的数
temp++;
}
if (temp == k) {
System.out.println(arr[i]);
}
}
}
}
}
//复杂度o(nlogn),先排序,然后相等的不输入,不等的计数加一,直到第k个不等的 #include<bits/stdc++.h> using namespace std; int main(){ int n; while(cin>>n){ int *a=new int[n],k,pos=1; for(int i=0;i<n;i++) cin>>a[i]; sort(a,a+n); cin>>k; if(k==1) cout<<a[0]; else{ for(int i=1;i<n;i++){ if(a[i]!=a[i-1]) pos++; if(pos==k){ cout<<a[i]<<endl; break; } } } } return 0; }
#include<iostream> #include<vector> #include<algorithm> using namespace std; int main(void) { int n; vector<int> a; while(cin >> n) { for(int i = 0;i < n;i++) { int x; cin >> x; a.push_back(x); } int k; cin >> k; sort(a.begin(),a.end()); int count = 0;//用来记数第K小的数 int max = 0; for(vector<int>::iterator it = a.begin();it != a.end();it++) { if(*it > max) { max = *it; count++; } if(count == k) break; } cout << max << endl; } return 0; }
#include<iostream> //#include<map>//map插入与搜索均是对数时间 #include<queue>//priority_queue查找最大值常数时间,插入对数时间 using namespace std; int main() { int n, k, x; while (cin>>n) { priority_queue<int, vector<int>, greater<int>> PQ; for (int i = 0; i < n; i++) { cin >> x; PQ.push(x); } cin >> k; x = PQ.top(); PQ.pop(); for (int i = 0; i < k - 1; i++) { if (PQ.size() > 0)//防止没有第K小的数 { if (PQ.top() == x) i--; else x = PQ.top(); PQ.pop(); } else break; } cout << x << endl; } return 0; }
#include<stdio.h> int a[1000],n; int min() { int min=a[0],i,j; for(i=1;i<n;i++)//找到最小的值 if(a[i]<min) min=a[i]; for(i=0;i<n;i++)//去重 if(a[i]==min) { for(j=i;j<n-1;j++) a[j]=a[j+1];//循环前移 n--; i--; } return min; } int main() { int m,i,key; scanf("%d",&n); for(i=0;i<n;i++) scanf("%d",&a[i]); scanf("%d",&m); while(m--) key=min(); printf("%d",key); }
#include<stdio.h> bool flag[1000]={0}; int main(){ int n,x,k,j; int cnt=0; scanf("%d",&n); int a[n]; for(int i=0;i<n;i++){ scanf("%d",&x); flag[x]=true; a[i]=x; } scanf("%d",&k); for(j=0;j<1000;j++){ if(flag[j]==true){ cnt++; if(cnt==k) break; } } printf("%d",j); }
import java.util.ArrayList; import java.util.Scanner; import java.util.TreeSet; public class Main { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); TreeSet<Integer> set = new TreeSet<>(); int n = scanner.nextInt(); for (int i = 0; i < n; i++) set.add(scanner.nextInt()); ArrayList<Integer> list = new ArrayList<>(set); int k = scanner.nextInt(); System.out.println(list.get(k-1)); } }
import java.util.Arrays; import java.util.Scanner; public class Main{ public static void main(String[] args) { Scanner scanner = new Scanner(System.in); while(scanner.hasNext()) { int n = scanner.nextInt(); int[] nums = new int[n]; for(int i = 0; i < n; i++) { nums[i] = scanner.nextInt(); } int min = scanner.nextInt(); Arrays.sort(nums); for(int i = 1; i < nums.length; i++) { if(nums[i] == nums[i - 1]) continue; min--; if(min == 1) { System.out.println(nums[i]); return; } } } } }
#include <stdio.h> int main() { int n; while(~scanf("%d",&n)) { int a[n],seq,min; for(int i=0;i<n;i++)scanf("%d",&a[i]); scanf("%d",&seq); for(int i=0;i<seq;i++) //进行seq次最小查找; { min=a[0]; for(int j=1;j<n;j++)if(min>a[j])min=a[j]; //查找当前序列最小值 for(int j=0;j<n && i!=seq-1;j++) //去重,当前最小值用尾部的值替换 { //最后一次查找不去重,因为没有意义 if(min==a[j]) { while(a[n-1]==min && n-1>j)n--; //注意数组末尾的数可能等于当前最小值! a[j]=a[n-1]; n--; } } } printf("%d\n",min); } }
#include<stdio.h> #include<algorithm> using namespace std; int buf[1001]; int main() { int n; while(scanf("%d",&n)!=EOF) { for(int i=0;i<n;i++) { scanf("%d",&buf[i]); } sort(buf,buf+n); int k; scanf("%d",&k); int count=1;//注意这里 int x=buf[0]; for(int i=1;count<k&&i<n;i++) { if(x<buf[i]) { count++; x=buf[i]; } } printf("%d\n",x); } return 0; }
#include <stdio.h> #include <stdlib.h> #include <string.h> //hash T(n)=O(n) int main() { int a[1000],n,i,x,count,y; while(scanf("%d",&n)!=EOF){ memset(a,0,sizeof(a)); for(i=0;i<n;i++){ scanf("%d",&x); a[x]=1; } scanf("%d",&y); count=0;i=0; while(count!=y){ if(a[i]!=0) count++; i++; } printf("%d\n",i-1); } }
import java.util.*; public class Main{ public static void main(String[] args){ int n; int[] a=new int[1000]; ArrayList<Integer> list=new ArrayList<Integer>(); HashMap<Integer,Integer> map=new HashMap<Integer,Integer>(); Scanner scanner=new Scanner(System.in); while(scanner.hasNext()){ n=scanner.nextInt(); for(int i=0;i<n;i++){ a[i]=scanner.nextInt(); if(!map.containsKey(a[i])){ map.put(a[i],1); list.add(a[i]); } } Collections.sort(list); int k; k=scanner.nextInt(); System.out.println(list.get(k-1)); } } }