ARST打卡第317周

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impl Solution {
    pub fn distribute_candies(n: i32, limit: i32) -> i64 {
        let mut ans: i64 = 0;
        for i in 0..=std::cmp::min(limit, n) {
            if n - i > 2 * limit {
                continue;
            }
            ans += std::cmp::min(n - i, limit) as i64 - std::cmp::max(0, n - i - limit) as i64 + 1;
        }

        return ans;
    }
}

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impl Solution {
    pub fn distribute_candies(n: i32, limit: i32) -> i64 {
        Self::cal(n + 2) - 3 * Self::cal(n - limit + 1) + 3 * Self::cal(n - (limit + 1) * 2 + 2) - Self::cal(n - 3 * (limit + 1) + 2)
    }

    fn cal(x: i32) -> i64 {
        if x < 0 {
            0
        } else {
            x as i64 * (x - 1) as i64 / 2
        }
    }
}