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.
Solution
- 类似
bit manipulate中的左移和右移来解决问题 - 左移: \(x = x / 10\)
- 右移: \(y = y * 10 + mod\)
- 注意防范overflow，先使用
long型，最后再转换成int型
Code(JAVA)
public int reverse(int x) {
long res = 0l;
while(x!=0){
res = res*10 + x%10;
if(res < Integer.MIN_VALUE || res> Integer.MAX_VALUE)
return 0;
x = x / 10;
}
return (int)res;
}
