Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++’s atoi function).
Constraints:
1.0 <= s.length <= 200 2.s consists of English letters (lower-case and upper-case), digits (0-9), ' ', '+', '-', and '.'.
Note:
Only the space character ' ' is considered a whitespace character.
Do not ignore any characters other than the leading whitespace or the rest of the string after the digits.
Example 1:
Input: s = "42" Output: 42
Example 2:
Input: s = " -42" Output: -42
Example 3:
Input: s = "4193 with words" Output: 4193
solution:
1.確認數值的正負狀態
如果是「+」，則default = 1
如果是「-」，則default = -1
2.確認數值是否為整數
移除前後空白
3.確認數值後是否有文字
移除不考慮
4.數值的處理
詳請月FlowChart
Code:
var myAtoi = function(s) {
// " -321321 bunnies"
//ignore leading whitespaces
let index = 0;
while (s[index] === " ") {
index++
}
//check if the next character is '-' or '+'
let sign = 1 //default to '+'
if (s[index] === '+') {
sign = 1
index++
} else if (s[index] === "-") {
sign = -1
index++
}
//read string of digits into integer
const digits = {}
for (let i = 0; i < 10; i++) {
digits[i + ""] = i
}
let result = 0
for (let i = index; i < s.length; i++) {
if (digits[s[i]] !== undefined) { // is digit
result = result * 10 + digits[s[i]] //重點
} else {
break
}
}
// clamped to max or min
result = result * sign
if (result < -1 * Math.pow(2, 31)) {
result = -1 * Math.pow(2, 31)
} else if (result > Math.pow(2, 31) -1) {
result = Math.pow(2, 31) -1
}
return result
};
FlowChart:
Example 1
result = 0 result = result * 10 + digits[s[i]] => 0 + 4 = 4 result = result * 10 + digits[s[i]] => 4 * 10 + 2 = 42
Output = 42
Example 2:
(s[count] === " ") => count = 1 (s[count] === " ") => count = 2 (s[count] === " ") => count = 3 (s[count] === " ") => count = 4 (s[count]) === "-") => default = -1;count = 5 result = 0 result = result * 10 + digits[s[i]] => 0 + 4 = 4 result = result * 10 + digits[s[i]] => 4 * 10 + 2 = 42 default * result = -1 * 42 => -42
Output = -42
Example 3:
result = 0 result = result * 10 + digits[s[i]] => 0 + 4 = 4 result = result * 10 + digits[s[i]] => 4 * 10 + 1 = 41 result = result * 10 + digits[s[i]] => 41 * 10 + 9 = 419 result = result * 10 + digits[s[i]] => 419 * 10 + 3 = 4193 (digits[s[i]] === underfined) => break
Output = 4193