刚学桶排序求助

这是WA的代码

# include<bits/stdc++.h>
using namespace std;
int a[1000], b;
int main(){
	int n, m;
	cin >> n >> m;
	for(int i = 1; i <= m; i++){
		cin >> b;
		a[b]++;
	}
	for(int i = 1; i <= m; i++)
		for(int j = 1; j <= a[i]; j++) 
			cout << i << " ";
	return 0;
}

这是用(sort)AC的代码

# include<bits/stdc++.h>
using namespace std;
int main(){
	int n, m;
	cin >> n >> m;
	int a[m];
	for(int i = 1; i <= m; i++)
		cin >> a[i];
	sort(a + 1, a + 1 + m);
	for(int i = 1; i <= m; i++)
		cout << a[i] << " ";
	return 0;
}