202. Happy Number
用HashSet存储已经出现过的数字，若重复出现肯定就不行了。
public boolean isHappy(int n) {
Set<Integer> inLoop = new HashSet<Integer>();
int squareSum,remain;
while (inLoop.add(n)) {
squareSum = 0;
while (n > 0) {
remain = n%10;
squareSum += remain*remain;
n /= 10;
}
if (squareSum == 1)
return true;
else
n = squareSum;
}
return false;
}
Set<Integer> inLoop = new HashSet<Integer>();
int squareSum,remain;
while (inLoop.add(n)) {
squareSum = 0;
while (n > 0) {
remain = n%10;
squareSum += remain*remain;
n /= 10;
}
if (squareSum == 1)
return true;
else
n = squareSum;
}
return false;
}