1056. Confusing Number
題目
A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.
We can rotate digits of a number by 180 degrees to form new digits.
When 0, 1, 6, 8, and 9 are rotated 180 degrees, they become 0, 1, 9, 8, and 6 respectively.
When 2, 3, 4, 5, and 7 are rotated 180 degrees, they become invalid.
Note that after rotating a number, we can ignore leading zeros.
For example, after rotating 8000, we have 0008 which is considered as just 8.
Given an integer n, return true if it is a confusing number, or false otherwise.
Example 1
Input: n = 6
Output: true
Explanation: We get 9 after rotating 6, 9 is a valid number, and 9 != 6.
Example 2
Input: n = 89
Output: true
Explanation: We get 68 after rotating 89, 68 is a valid number and 68 != 89.
Example 3
Input: n = 11
Output: false
Explanation: We get 11 after rotating 11, 11 is a valid number but the value remains the same, thus 11 is not a confusing number
Constraints:
- 0 <= n <= 109
先根據題目給的內容建立 mapping 表。在將題目倒轉，確認倒轉後的數值是否和原本相同。
題目難易度
Easy
解題想法
為了方便做每個字元的 mapping 確認，mapping 表均是使用字串，而題目給的部分翻轉會是invalid的字元，則用 null 表示。
先將題目給的字串反轉，接下來一個一個確認每個字元，若遇到題目給的 mapping 出來會是invalid的則直接回傳 false。
若均無invalid的狀況，則最後將所有 mapping 完的字元組成字串去比較和原本題目給的數值轉為字串是否相同。
初試
Runtime: 63ms, 80%
Memory Usage: 41.8MB, 76%
/**
* @param {number} n
* @return {boolean}
*/
var confusingNumber = function (n) {
const rMap = new Map([
["0", "0"],
["1", "1"],
["6", "9"],
["8", "8"],
["9", "6"],
["2", null],
["3", null],
["4", null],
["5", null],
["7", null],
]);
const nArrayR = n.toString().split("").reverse();
const xxA = [];
for (let i = 0; i < nArrayR.length; i++) {
const target = rMap.get(nArrayR[i]);
if (target === null) {
return false;
}
xxA.push(target);
}
return xxA.join("") === n.toString() ? false : true;
};