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:
- n = 5
- The coins can form the following rows:
- ¤
- ¤ ¤
- ¤ ¤
- Because the 3rd row is incomplete, we return 2.
- n = 8
- The coins can form the following rows:
- ¤
- ¤ ¤
- ¤ ¤ ¤
- ¤ ¤
- Because the 4th row is incomplete, we return 3.
C Solution 1:
int arrangeCoins(int n) {
int i = 1;
while (n >= i) {
n -= i++;
}
return i - 1;
}
C Solution 2:
int arrangeCoins(int n) {
int l = 1, r = n;
while (l <= r) {
int m = l + (r - l) / 2;
if (0.5 * m * m + 0.5 * m <= n) {
l = m + 1;
}
else r = m - 1;
}
return l - 1;
}
C Solution 3:
int arrangeCoins(int n) {
return sqrt(2.0 * n + 0.25) - 0.5;
}
Summary:
- 22ms, 42.06%
- Binary search is strange, because of double?
LeetCode: 441. Arranging Coins
近期评论