g1901_2000.s1922_count_good_numbers.Solution Maven / Gradle / Ivy
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Java Solution for LeetCode algorithm problems, continually updating
package g1901_2000.s1922_count_good_numbers;
// #Medium #Math #Recursion #2022_05_14_Time_1_ms_(87.11%)_Space_40.6_MB_(68.56%)
public class Solution {
public int countGoodNumbers(long n) {
long mod = 1000000007L;
long result = n % 2 == 0 ? 1L : 5L;
long base = 20L;
long time = n / 2L;
while (time > 0) {
if (time % 2L > 0) {
result *= base;
result %= mod;
}
time /= 2L;
base = base * base % mod;
}
return (int) result;
}
}