# my C++ 9ms solution

• ``````#include <vector>
using namespace std;

class Solution {
public:
bool makesquare(vector<int>& nums) {
n = nums.size() + 1;

long long sum = 0, a;
for (int x : nums)
sum += x;
if (sum % 4 != 0)
return false;
a = sum / 4;

vector<int> ans;
choice(0, nums, ans, 0, a);
int m = ans.size();
int ai, aj, ak, al;
for (int i = 0; i < m; ++i) {
ai = ans[i];
for (int j = i + 1; j < m; ++j) {
aj = ans[j];
if (ai & aj)
continue;
aj |= ai;
for (int k = j + 1; k < m; ++k) {
ak = ans[k];
if (aj & ak)
continue;
ak |= aj;
for (int l = k + 1; l < m; ++l) {
al = ans[l];
if (ak & al)
continue;
return true;
}
}
}
}
return false;
}
private:
int n;
void choice(int choc, vector<int>& nums, vector<int>& ans, int depth, int rest)
{
if (rest == 0) {
ans.push_back(choc);
return;
}
if (depth == n)
return;

int w = nums[depth];
if (rest >= w) {
choice(choc | (1 << depth), nums, ans, depth + 1, rest - w);
}
choice(choc, nums, ans, depth + 1, rest);
}
};
``````

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