441. Arranging Coins
You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins.
Given n, find the total number of full staircase rows that can be formed.
n is a non-negative integer and fits within the range of a 32-bit signed integer.
Example 1:
n = 5 The coins can form the following rows: ¤ ¤ ¤ ¤ ¤ Because the 3rd row is incomplete, we return 2.
Example 2:
n = 8 The coins can form the following rows: ¤ ¤ ¤ ¤ ¤ ¤ ¤ ¤ Because the 4th row is incomplete, we return 3.
Rust Solution
struct Solution;
impl Solution {
fn arrange_coins(n: i32) -> i32 {
(((2 * n as i64) as f64 + 0.25).sqrt() - 0.5).floor() as i32
}
}
#[test]
fn test() {
assert_eq!(Solution::arrange_coins(5), 2);
assert_eq!(Solution::arrange_coins(8), 3);
assert_eq!(Solution::arrange_coins(1_804_289_383), 60070);
}
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