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.
每增加一层,星星就多一个，而n就要多减上一层的星星数+1,最后n不够减了说明最后一层不作数。
1 int arrangeCoins(int n) { 2 int i=0; 3 while(n>0){ 4 i+=1; 5 n-=i; 6 } 7 return n==0?i:i-1; 8 }