Description
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:
Solutions
Solution 1
PythonJavaC++GoTypeScriptRustC
class Solution:
def isHappy(self, n: int) -> bool:
vis = set()
while n != 1 and n not in vis:
vis.add(n)
x = 0
while n:
n, v = divmod(n, 10)
x += v * v
n = x
return n == 1(code-box)
class Solution {
public boolean isHappy(int n) {
Set<Integer> vis = new HashSet<>();
while (n != 1 && !vis.contains(n)) {
vis.add(n);
int x = 0;
while (n != 0) {
x += (n % 10) * (n % 10);
n /= 10;
}
n = x;
}
return n == 1;
}
}(code-box)
class Solution {
public:
bool isHappy(int n) {
unordered_set<int> vis;
while (n != 1 && !vis.count(n)) {
vis.insert(n);
int x = 0;
for (; n; n /= 10) {
x += (n % 10) * (n % 10);
}
n = x;
}
return n == 1;
}
};(code-box)
func isHappy(n int) bool {
vis := map[int]bool{}
for n != 1 && !vis[n] {
vis[n] = true
x := 0
for ; n > 0; n /= 10 {
x += (n % 10) * (n % 10)
}
n = x
}
return n == 1
}(code-box)
function isHappy(n: number): boolean {
const getNext = (n: number) => {
let res = 0;
while (n !== 0) {
res += (n % 10) ** 2;
n = Math.floor(n / 10);
}
return res;
};
const set = new Set();
while (n !== 1) {
const next = getNext(n);
if (set.has(next)) {
return false;
}
set.add(next);
n = next;
}
return true;
}(code-box)
use std::collections::HashSet;
impl Solution {
fn get_next(mut n: i32) -> i32 {
let mut res = 0;
while n != 0 {
res += (n % 10).pow(2);
n /= 10;
}
res
}
pub fn is_happy(mut n: i32) -> bool {
let mut set = HashSet::new();
while n != 1 {
let next = Self::get_next(n);
if set.contains(&next) {
return false;
}
set.insert(next);
n = next;
}
true
}
}(code-box)
int getNext(int n) {
int res = 0;
while (n) {
res += (n % 10) * (n % 10);
n /= 10;
}
return res;
}
bool isHappy(int n) {
int slow = n;
int fast = getNext(n);
while (slow != fast) {
slow = getNext(slow);
fast = getNext(getNext(fast));
}
return fast == 1;
}(code-box)
Solution 2
PythonJavaC++GoTypeScriptRust
class Solution:
def isHappy(self, n: int) -> bool:
def next(x):
y = 0
while x:
x, v = divmod(x, 10)
y += v * v
return y
slow, fast = n, next(n)
while slow != fast:
slow, fast = next(slow), next(next(fast))
return slow == 1(code-box)
class Solution {
public boolean isHappy(int n) {
int slow = n, fast = next(n);
while (slow != fast) {
slow = next(slow);
fast = next(next(fast));
}
return slow == 1;
}
private int next(int x) {
int y = 0;
for (; x > 0; x /= 10) {
y += (x % 10) * (x % 10);
}
return y;
}
}(code-box)
class Solution {
public:
bool isHappy(int n) {
auto next = [](int x) {
int y = 0;
for (; x; x /= 10) {
y += pow(x % 10, 2);
}
return y;
};
int slow = n, fast = next(n);
while (slow != fast) {
slow = next(slow);
fast = next(next(fast));
}
return slow == 1;
}
};(code-box)
func isHappy(n int) bool {
next := func(x int) (y int) {
for ; x > 0; x /= 10 {
y += (x % 10) * (x % 10)
}
return
}
slow, fast := n, next(n)
for slow != fast {
slow = next(slow)
fast = next(next(fast))
}
return slow == 1
}(code-box)
function isHappy(n: number): boolean {
const getNext = (n: number) => {
let res = 0;
while (n !== 0) {
res += (n % 10) ** 2;
n = Math.floor(n / 10);
}
return res;
};
let slow = n;
let fast = getNext(n);
while (slow !== fast) {
slow = getNext(slow);
fast = getNext(getNext(fast));
}
return fast === 1;
}(code-box)
impl Solution {
pub fn is_happy(n: i32) -> bool {
let get_next = |mut n: i32| {
let mut res = 0;
while n != 0 {
res += (n % 10).pow(2);
n /= 10;
}
res
};
let mut slow = n;
let mut fast = get_next(n);
while slow != fast {
slow = get_next(slow);
fast = get_next(get_next(fast));
}
slow == 1
}
}(code-box)
