Solve problem '202) happy number'

problems/202-happy-number/README.md

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+Write an algorithm to determine if a number `n` is happy.
+
+A **happy number** is a number defined by the following process:
+
+- Starting with any positive integer, replace the number by the sum of the squares of its digits.
+- Repeat the process until the number equals 1 (where it will stay), or it **loops endlessly in a cycle** which does not include 1.
+- Those numbers for which this process **ends in 1** are happy.
+
+Return `true` if `n` _is a happy number, and_ `false` if not.
+
+**Example 1:**
+
+```
+Input: n = 19
+Output: true
+Explanation:
+12 + 92 = 82
+82 + 22 = 68
+62 + 82 = 100
+12 + 02 + 02 = 1
+```
+
+**Example 2:**
+
+```
+Input: n = 2
+Output: false
+```
+
+**Constraints:**
+
+- 1 <= n <= 2^31 - 1

problems/202-happy-number/main.go

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+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println(isHappy(19))
+	fmt.Println(isHappy(2))
+}
+
+func isHappy(n int) bool {
+	if n == 0 {
+		return false
+	}
+	res := 0
+	num := n
+	record := map[int]int{}
+	for {
+		for num != 0 {
+			res += (num % 10) * (num % 10)
+			num = num / 10
+		}
+		if _, ok := record[res]; !ok {
+			if res == 1 {
+				return true
+			}
+			record[res] = res
+			num = res
+			res = 0
+			continue
+		} else {
+			return false
+		}
+	}
+}