Perfect Number
一个数是Perfect number就是他的factor的和等于这个数. 那么先求factor, 然后求和就可以了.
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class Solution { public boolean checkPerfectNumber(int num) { if(num <= 0) return false; int sum = 0; for(int i = 1; i <= Math.sqrt(num); i++) { if(num % i == 0) { // if it is a factor sum += i; if (i * i != num) { // adding num / i sum += num / i; } } } System.out.println(sum); return sum - num == num; } } |