C++二维数组vector的排序

#include<algorithm>
int main()
{
	vector<vector<int>>ans;
	ans.push_back({ 6,7,8 });
	ans.push_back({ 5,6 });

	sort(ans.begin(), ans.end(), [](vector<int>a, vector<int>b) {return a[0] < b[0]; });


	return 0;
}