Q7. Reverse Integer
直达:https://leetcode.com/problems/reverse-integer/description/
iven 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 hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
分析
保存正负号后使用绝对值进行运算。
使用 %10取个位,使用 /10进行右移1位。
使用长整型保存结果(Python不用)以便进行溢出判断。
代码
C++
class Solution {
public:
int reverse(int x) {
if (x == INT_MIN) return 0;
int sign = x>0?1:-1;
x = sign * x;
double res = 0;
while(x != 0){
res *= 10;
res += x%10;
x /= 10;
}
if ( (sign > 0 && res > INT_MAX) || (sign < 0 && res-1 > INT_MAX) ) return 0;
else return sign * int(res);
}
};
python
class Solution(object):
def reverse(self, x):
"""
:type x: int
:rtype: int
"""
pos_x = abs(x)
res = 0
while(pos_x > 0):
res *= 10
res += pos_x%10
pos_x = pos_x/10
if(x < 0):
res = -res
if abs(res) > 0x7FFFFFFF:
return 0
else:
return res
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