题目
We define the Perfect Number is a positive integer that is equal to the sum of all its positive divisors except itself.
Now, given an integer n, write a function that returns true when it is a perfect number and false when it is not.
Example:
Input: 28
Output: True
Explanation: 28 = 1 + 2 + 4 + 7 + 14
Note:
The input number n will not exceed 100,000,000. (1e8)
解题思路
- 求出输入值num的平方根sqrt1
- 判断num能否将i （i属于[2, sqrt1]）整除，如果可以，则将i和num/i加入num的因数和sum中
- 判断num和sum是否相等，如果相等，则为完美数，否则不是
注意
因子不包括自己，所以如果输入是1的话，因子不能有1，1不是完美数
代码
perfectNumber.go
package _507_Perfect_Number
import "math"
func CheckPerfectNumber(num int) bool {
if 1 == num {
return false
}
sqrt1 := int(math.Sqrt(float64(num)))
var sum int
sum = 1
for i := 2; i <= sqrt1; i++ {
if num % i == 0 {
sum += i
sum += num /i
}
}
if sum == num {
return true
}
return false
}
测试
perfectNumber_test.go
package _507_Perfect_Number
import "testing"
func TestCheckPerfectNumber(t *testing.T) {
var tests = []struct{
num int
ret bool
} {
{6, true},
{28, true},
{1, false},
}
for _, v := range tests {
ret := CheckPerfectNumber(v.num)
if ret == v.ret {
t.Logf("pass")
} else {
t.Errorf("fail, want %+v, get %+v", v.ret, ret)
}
}
}
