pub fn next_permutation(nums: &mut Vec<i32>) {

let N = nums.len();

let mut i = N - 1;

while i > 0 && nums[i] <= nums[i-1] {

i -= 1;

}

if i == 0 {

nums.sort();

return;

}

let left = i - 1;

let mut right = left + 1;

while right < N && nums[left] < nums[right] {

right += 1;

}

nums.swap(left, right - 1);

nums[left+1..].sort()

}