在此提供三種解法，其實三種解法殊途同歸，不就是排個序，去個重就好！

1.利用map特點，插入map之後，會自動根據關鍵字排序，而且不會出現相同的關鍵字，正好滿足特性

#include<iostream>
#include<map>
using namespace std;
int main()
{
	map<int, int> in;
	int num, temp;
	cin >> num;
	for (int i = 0; i<num; i++)
	{
		cin >> temp;
		in[temp]++;
	}

	for (map<int, int>::iterator iter=in.begin(); iter != in.end(); iter++)
	{
		cout << iter->first << endl;
	}
	return 0;
}
 

#include<iostream>
using namespace std;

int main()
{
	int hash[1001], count, num;
	memset(hash, 0, sizeof(int)* 1001);

	cin >> count;
	for (int i = 0; i<count; i++)
	{
		cin >> num;
		hash[num]++;
	}

	for (int i = 1; i <= 1000; i++)
	{
		if (hash[i]>0)
		{
			cout << i << endl;
		}
	}
	return 0;
}
 

#include<iostream>
#include<algorithm>
using namespace std;

int main()
{
	int stack[100], count, num,j,k;

	cin >> count;
	for (int i = 0; i < count; i++)
	{
		cin >> num;
		stack[i] = num;
	}

	sort(stack, stack + count);

	for (j = 0, k = 0; k < count;)
	{
		if (stack[j] == stack[k])
		{
			k++;
		}
		else
		{
			cout << stack[j] << endl;
			j = k;
		}
	}

	cout << stack[count-1] << endl;

	return 0;
}
 

#include<iostream>
using namespace std;
int main()
{
	char in[100];
	gets_s(in);
	int len = strlen(in);
	int count = 0;
	char temp;
	cin >> temp;
	for (int i = 0; i < len; i++)
	{
		if (in[i] == temp||in[i]==temp+32||in[i]==temp-32)
		{
			count++;
		}
	}
	cout << count << endl;
	return 0;
}