Given a 32-bit signed integer, reverse digits of an integer.
// 32-bite
// Math.pow(2, 31);
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.
*/
/**
* 一個一個拉出來換
* 321 for example
* get 1 result = 1
* get 2 result = 1*10 + 2
* get 3 result = 12+10 + 3
// 完全不同方向思考
*/
/**
* @param {number} x
* @return {number}
*/
var reverse = function(x) {}
怎麼解
數字一個一個拉出來換，從後面開始(個位數)．例如 321
get 1 result = 321%10 = 1
get 2 result = Math.floor( 321/10) % 10
get 3 result = Math.floor(321/ 100) % 10
var reverse = function(x) {
let INT_MAX = Math.pow(2, 31);
let reverse = 0;
// save negative or not
let flag = x > 0 ? 1 : -1;//
x = Math.abs(x);
while(x != 0) {
reverse = reverse*10 + x%10;
x = Math.floor(x/10);
}
if(reverse > INT_MAX || reverse < INT_MAX*-1){
return 0;
}
return reverse*flag;
};