re order 11 and 12

labs/12_hash_tables/test3/happy_number_set_sol.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+#include <unordered_set>
+
+int replace(int n){
+	int digit;
+	int result=0;
+	while(n>0){
+		digit = (n%10);
+		result += digit * digit;
+		n = n/10;
+	}
+	return result;
+}
+
+bool isHappy(int n) {
+	int newN = n;
+	std::unordered_set<int> set1;
+	while(1){
+		newN = replace(newN);
+		if(newN==1){
+			return true;
+		}else{
+			// if we can find it, this is going to be an infinite loop
+			if(set1.find(newN)!=set1.end()){
+				return false;
+			}
+			// can't find it, insert it in the set first
+			set1.insert(newN);
+		}
+	}
+}
+
+int main() {
+	// Test cases
+	// 2, 4, 5, 6, 17, 18, 20 are not happy numbers.
+	// 1, 7, 10, 13, 19, 23, 28, 68 are not happy numbers.
+
+    int testCases[] = {2,4,5,6,17,18,20,1,7,10,13,19,23,28,68};
+
+    for (int n : testCases) {
+        if (isHappy(n)) {
+            std::cout << n << " is a happy number." << std::endl;
+        } else {
+            std::cout << n << " is not a happy number." << std::endl;
+        }
+    }
+
+    return 0;
+}
+