Leftmost Digit
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 15305 Accepted Submission(s): 5937
Problem Description
Given a positive integer N, you should output the leftmost digit of N^N.
Input
The input contains several test cases. The first line of the input is a single integer T which is the number of test cases. T test cases follow. Each test case contains a single positive integer N(1<=N<=1,000,000,000).
Output
For each test case, you should output the leftmost digit of N^N.
Sample Input
2
3
4
Sample Output
2
2
Hint
In the first case, 3 * 3 * 3 = 27, so the leftmost digit is 2. In the second case, 4 * 4 * 4 * 4 = 256, so the leftmost digit is 2.
Author
Ignatius.L
Solution
取对数。
设 n^n = x*10^y(n^n的科学计数法表示),
则 log (n^n) = y + log x
Implementation
#includeusing namespace std;int main(){ int T; scanf("%d", &T); for(int n; T--; ){ scanf("%d", &n); double t=log10(n)*n; printf("%d\n",(int)pow(10, t-floor(t))); }}
Tips
<cmath>内常用函数:
pow
exp
log 自然对数
log10 常用对数
log2 以2为底的对数
floor
ceil