Java 解法, 执行用时: 735ms, 内存消耗: 39848K, 提交时间: 2021-10-10 23:57:27

import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(), sum = 0;
        int[] arr = new int[1000005];
        for (int i = 0; i < n; i++) {
            int t = in.nextInt();
            if (arr[t] == 0) {
                arr[t] = 1;
                sum++;
            }
        }
        System.out.println(sum);
    }
}

C++14(g++5.4) 解法, 执行用时: 34ms, 内存消耗: 4836K, 提交时间: 2020-05-10 14:15:36

#include<bits/stdc++.h>
using namespace std;
int m,n,i,j,ans;
int a[100010],vis[1000010];
int main()
{
	scanf("%d",&n);
	for(i=1;i<=n;i++)
	{
		scanf("%d",&a[i]);
		if(!vis[a[i]])
		{
			vis[a[i]]=1;
			ans++;
		}
	}
	printf("%d\n",ans);
	return 0;
}

C++11(clang++ 3.9) 解法, 执行用时: 28ms, 内存消耗: 4448K, 提交时间: 2020-05-10 14:16:44

#include<bits/stdc++.h>
using namespace std;
unsigned int a[1000005];
int main()
{
	int n,sum=0;
	scanf("%d",&n);
	while(n--)
	{
		int i;
		scanf("%d",&i);
		if(a[i]==0)
		{
			a[i]=1;
			sum++;
		}
	}
	printf("%d\n",sum);
}