自己的三十行模拟：

#include<iostream>
#include<cstring>
#include<algorithm>
#include<math.h>
using namespace std;

int main() {
	unsigned int n,sum=1,t=0;
	int a[16], b[16];
	cin >> n;
	for (int i = 0; i < 16; ++i) {
		a[i] = n & 1;
		n>>= 1;//不要忘记等于
	}
	for (int i = 0; i < 16; ++i) {
		b[i] = n & 1;
		n >>= 1;
	}
	for (int i = 0; i < 16; ++i) {
		if (b[i])
			t += sum;
		sum *=2;
	}
	for (int i = 0; i < 16; ++i) {
		if (a[i])
			t += sum;
		sum *=2;
	}
	cout << t << endl;//越界的时候无符号数为0
}

看洛谷大佬题解后：十行

#include<iostream>
#include<cstring>
#include<algorithm>
#include<math.h>
using namespace std;

int main() {
	unsigned int n;
	cin >> n;
	//注意左移后移的优先级
	cout << (n << 16) + (n >> 16) << endl;
}