pub fn generate(num_rows: i32) -> Vec<Vec<i32>> {

let mut ans = vec![];

let mut curr = vec![1];

for i in 0..num_rows {

let mut next = vec![1];

for i in 0..curr.len()-1 {

next.push(curr[i] + curr[i+1]);

}

next.push(1);

ans.push(curr);

curr = next;

}

ans

}