solve #202

Author: aylei

src/lib.rs

@@ -169,3 +169,4 @@ mod n0198_house_robber;
 mod n0199_binary_tree_right_side_view;
 mod n0200_number_of_islands;
 mod n0201_bitwise_and_of_numbers_range;
+mod n0202_happy_number;

src/n0202_happy_number.rs

@@ -0,0 +1,65 @@
+/**
+ * [202] Happy Number
+ *
+ * Write an algorithm to determine if a number 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, and 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 numbers.
+ * 
+ * Example: 
+ * 
+ * 
+ * Input: 19
+ * Output: true
+ * Explanation: 
+ * 1^2 + 9^2 = 82
+ * 8^2 + 2^2 = 68
+ * 6^2 + 8^2 = 100
+ * 1^2 + 0^2 + 0^2 = 1
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+use std::collections::HashSet;
+impl Solution {
+    pub fn is_happy(n: i32) -> bool {
+        let mut set = HashSet::new();
+        let mut n = n;
+        loop {
+            set.insert(n);
+            let temp = Solution::next(n);
+            if temp == 1 {
+                return true
+            }
+            if !set.insert(temp) {
+                return false
+            }
+            n = temp
+        }
+        return false
+    }
+
+    fn next(n: i32) -> i32 {
+        let mut res = 0;
+        let mut n = n;
+        while n != 0 {
+            res += (n % 10).pow(2);
+            n = n / 10;
+        }
+        res
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_202() {
+        assert_eq!(Solution::is_happy(19), true);
+        assert_eq!(Solution::is_happy(235123), false);
+    }
+}