못생긴 숫자는 소인수가 2, 3 또는 5인 숫자입니다. 1부터 15까지 11개의 못생긴 숫자 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15. 7, 11, 13은 소수이기 때문에 못생긴 것이 아닙니다. 숫자 14는 소인수에 7이 올 것이기 때문에 못생긴 것이 아닙니다.
이 프로그램에서 우리는 n번째 못생긴 숫자를 찾으려고 노력할 것입니다.
입력 및 출력
Input: Take the term number. Say it is 10 Output: The 10th ugly number is 12
알고리즘
getUglyNumbers(n)
입력: 용어의 수입니다.
출력: n번째 못생긴 숫자를 찾습니다.
Begin define array named uglyNum of size n i2 := 0, i3 := 0, i5 := 0 next2mul := 2, next3mul := 3, next5Mul := 5 next := 1 ugluNum[0] := 1 for i := 1 to n, do next := minimum of next2Mul, next3Mul and next5Mul uglyNum[i] := next if next = next2Mul, then i2 := i2 + 1 next2mul := uglyNum[i2] * 2 if next = next3Mul, then i3 := i3 + 1 next3mul := uglyNum[i3] * 3 if next = next5Mul, then i5 := i5 + 1 next5mul := uglyNum[i5] * 5 done return next End
예시
# include<iostream> using namespace std; int min(int x, int y, int z) { //find smallest among three numbers if(x < y) { if(x < z) return x; else return z; }else { if(y < z) return y; else return z; } } int getUglyNum(int n) { int uglyNum[n]; // To store ugly numbers int i2 = 0, i3 = 0, i5 = 0; //find next multiple as 1*2, 1*3, 1*5 int next2mul = 2; int next3mul = 3; int next5mul = 5; int next = 1; //initially the ugly number is 1 uglyNum[0] = 1; for (int i=1; i<n; i++) { next = min(next2mul, next3mul, next5mul); //find next ugly number uglyNum[i] = next; if (next == next2mul) { i2++; //increase iterator of ugly numbers whose factor is 2 next2mul = uglyNum[i2]*2; } if (next == next3mul) { i3++; //increase iterator of ugly numbers whose factor is 3 next3mul = uglyNum[i3]*3; } if (next == next5mul) { i5++; //increase iterator of ugly numbers whose factor is 5 next5mul = uglyNum[i5]*5; } } return next; //the nth ugly number } int main() { int n; cout << "Enter term: "; cin >> n; cout << n << "th Ugly number is: " << getUglyNum(n) << endl; }
출력
Enter term: 10 10th Ugly number is: 12