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Leetcode 运行输出与本地结果不一样的解决方法（用例子说明）
目录[-]
Problem：
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: 19 is a happy number
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
Thought：
The idea is just simple, the hints of HashMap and Recursion will help you a lot.
Java Solution（ Wrong Answer）
public class Solution {
private static Map<Integer, Integer> map = new HashMap<Integer, Integer>();
public boolean isHappy(int n) {
if (n == 1) {
return true;
} else if (map.containsKey(n)) {
return false;
} else {
map.put(n, map.size());
}
String str = n + "";
char[] c = str.toCharArray();
int temp = 0;
for (int i = 0; i < c.length; i++) {
temp += Integer.parseInt(c[i]+"") * Integer.parseInt(c[i]+"");
}
// recursion
return isHappy(temp);
}
}
Exception
But the problem is that the answer of LeetCode is different from that of local IDE, which means when I iuput 10 in my local IDE, the output is true. Details is in the picture below: 
The solution is : try to declare the class variables as class instance variables instead of class staic variables; That’s because the judger runs all test cases in one go.
Reference:https://leetcode.com/discuss/5800/different-answer-between-local-idle-and-leetcode?show=5800#q5800
Java Solution（ Accepted）
public class Solution{
// Don't declare the variable as a static one, or it will occur error when OJ;
private Map<Integer, Integer> map = new HashMap<Integer, Integer>();
public boolean isHappy(int n) {
// print just for testing
// System.out.println(n);
if (n == 1) {
return true;
} else if (map.containsKey(n)) {
return false;
} else {
map.put(n, map.size());
}
String str = n + "";
char[] c = str.toCharArray();
int temp = 0;
for (int i = 0; i < c.length; i++) {
temp += Integer.parseInt(c[i]+"") * Integer.parseInt(c[i]+"");
}
// recursion
return isHappy(temp);
}
}
Online Judge: Happy Number
If you have any questions or any bugs are found, please feel free to contact me.
Your comments and suggestions are welcome!
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