Add problem 507

Author: avhn

algorithms/507/README.md

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+## 507. Perfect Number
+
+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:**
+<pre>
+<b>Input:</b> 28
+<b>Output:<b> True
+<b>Explanation:</b> 28 = 1 + 2 + 4 + 7 + 14
+</pre>
+
+**Note:** The input number **n** will not exceed 100,000,000. (1e8)

algorithms/507/solution.go

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+package main
+
+import "math"
+
+func checkPerfectNumber(num int) bool {
+if num < 2 {
+return false
+}
+sum := 1
+for i := 2; i <= int(math.Sqrt(float64(num))); i++ {
+if num%i == 0 {
+sum += i + num/i
+}
+}
+return sum == num
+}