11462 Age Sort
You are given the ages (in years) of all people of a country with at least 1 year of age. You know that
no individual in that country lives for 100 or more years. Now, you are given a very simple task of
sorting all the ages in ascending order.
Input
There are multiple test cases in the input ?le. Each case starts with an integer n (0 < n ≤ 2000000), the
total number of people. In the next line, there are n integers indicating the ages. Input is terminated
with a case where n = 0. This case should not be processed.
Output
For each case, print a line with n space separated integers. These integers are the ages of that country
sorted in ascending order.
Warning: Input Data is pretty big (∼ 25 MB) so use faster IO.
Sample Input
5
3 4 2 1 5
5
2 3 2 3 1
0
Sample Output
1 2 3 4 5
1 2 2 3 3

思路：计数排序

AC代码1（519ms）：

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

int main()
{
	int x, n, c[101];
	while(scanf("%d", &n) == 1 && n)
	{
		memset(c, 0, sizeof(c));
		for(int i=0; i<n; i++)
		{
			scanf("%d", &x);
			c[x]++;
		}
		int flag = 1;
		for(int i=1; i<=100; i++)
			for(int j=0; j<c[i]; j++)
			{
				if(!flag) printf(" ");
				flag = 0;
				printf("%d", i);
			}
		printf("\n");
	} 
	return 0;
}

AC代码2（172ms）：

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cctype>      //为了使用isdigit宏 
using namespace std;

inline int readint()
{
	char c = getchar();
	while(!isdigit(c)) c = getchar();
	
	int x = 0;
	while(isdigit(c))
	{
		x = x * 10 + c - '0';
		c = getchar();
	}
	return x;
}

int buf[10];		//声明成全局变量可以减小开销 
inline void writeint(int i)
{
	int p = 0;
	if(i == 0) p++;		//特殊情况：i等于0的时候需要输出0，而不是什么也不输出 
	else while(i)
	{
		buf[p++] = i % 10;
		i /= 10;
	}
	for(int j = p-1; j >= 0; j--) putchar('0' + buf[j]);	//逆序输出 
}

int main()
{
	int n, x, c[101];
	while(n = readint())
	{
		memset(c, 0, sizeof(c));
		for(int i = 0; i < n; i++) c[readint()]++;
		int flag = 1;
		for(int i = 1; i <= 100; i++)
			for(int j=0; j < c[i]; j++)
			{
				if(!flag) putchar(' ');
				flag = 0;
				writeint(i);
			}
		putchar('\n');
	}
	return 0;
}

UVA - 11462 - Age Sort （高效算法！！）