A. Maximum Square
Ujan decided to make a new wooden roof for the house. He has ???? rectangular planks numbered from 1 to ????. The ????-th plank has size ????????×1 (that is, the width is 1 and the height is ????????).
Now, Ujan wants to make a square roof. He will first choose some of the planks and place them side by side in some order. Then he will glue together all of these planks by their vertical sides. Finally, he will cut out a square from the resulting shape in such a way that the sides of the square are horizontal and vertical.
For example, if Ujan had planks with lengths 4, 3, 1, 4 and 5, he could choose planks with lengths 4, 3 and 5. Then he can cut out a 3×3 square, which is the maximum possible. Note that this is not the only way he can obtain a 3×3 square.
What is the maximum side length of the square Ujan can get?
Input
The first line of input contains a single integer ???? (1≤????≤10), the number of test cases in the input.
For each test case, the first line contains a single integer ???? (1≤????≤1000), the number of planks Ujan has in store. The next line contains ???? integers ????1,…,???????? (1≤????????≤????), the lengths of the planks.
Output
For each of the test cases, output a single integer, the maximum possible side length of the square.
Example
input
4
5
4 3 1 4 5
4
4 4 4 4
3
1 1 1
5
5 5 1 1 5
output
3
4
1
3
Note
The first sample corresponds to the example in the statement.
In the second sample, gluing all 4 planks will result in a 4×4 square.
In the third sample, the maximum possible square is 1×1 and can be taken simply as any of the planks.
题意
现在有n个栏杆，现在想要从里面切割出一个最大的正方形，问正方形的边长最大是多少。
题解
我们按照从小到大对栏杆长度进行排序，然后我们暴力枚举正方形的边长，然后看最大的是多少就可以了。
代码
#include<bits/stdc++.h>
using namespace std;
const int maxn =1005;
int n,a[maxn];
void solve(){
scanf("%d",&n);
for(int i=0;i<n;i++){
scanf("%d",&a[i]);
}
sort(a,a+n);
int ans = 0;
for(int i=0;i<n;i++){
for(int j=a[i];j>=0;j--){
if((n-i)>=j){
ans=max(ans,j);
break;
}
}
}
cout<<ans<<endl;
}
int main(){
int t;
scanf("%d",&t);
while(t--)solve();
}
