struct Solution;
impl Solution {
fn three_sum_smaller(mut nums: Vec<i32>, target: i32) -> i32 {
nums.sort_unstable();
let n = nums.len();
let mut res = 0;
for i in 0..n {
let mut j = i + 1;
let mut k = n - 1;
while j < k {
if nums[i] + nums[j] + nums[k] < target {
res += k - j;
j += 1;
} else {
k -= 1;
}
}
}
res as i32
}
}
#[test]
fn test() {
let nums = vec![-2, 0, 1, 3];
let target = 2;
let res = 2;
assert_eq!(Solution::three_sum_smaller(nums, target), res);
}