leetcode 7. Reverse Integer
Given a 32-bit signed integer, reverse digits of an integer.Example 1:
Input: 123
Output: 321
Example 2:
Input: -123
Output: -321
Example 3:
Input: 120
Output: 21
Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
First try
import java.math.BigInteger;
class Solution {
public int reverse(int x) {
String num = Integer.toString(x);
String result = "";
int len = num.length();
int flag = 0;
if(num.substring(0,1).equals("-")){
flag = 1;
num = num.substring(1,len);
len = len -1;
}
for(int i = 0 ; i< len; i++){
result = num.substring(i,i+1) + result;
}
BigInteger n = new BigInteger(result);
BigInteger s = new BigInteger("-2147483648");
BigInteger b = new BigInteger("2147483647");
if(n.compareTo(s)<0|| n.compareTo(b)>0){
return 0;
}
x = Integer.parseInt(result);
if(flag == 1){
return 0-x;
}
else{
return x;
}
}
}
Second try.
class Solution {
public int reverse(int x) {
long result = 0;
while(x != 0){
result = result * 10 + x % 10;
x = x/10;
}
if(result > 2147483647 || result < -2147483648)
return 0;
return (int)result;
}
}
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