Easy Math String
Implement atoi which converts a string to an integer.
The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.
The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.
If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.
If no valid conversion could be performed, a zero value is returned.
Note:
Only the space character ' ' is considered as whitespace character. Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. If the numerical value is out of the range of representable values, INT_MAX (231 − 1) or INT_MIN (−231) is returned.
Example1:
Input: "42"
Output: 42
Example2:
Input: " -42"
Output: -42
Explanation: The first non-whitespace character is '-', which is the minus sign.Then take as many numerical digits as possible, which gets 42.
Example3:
Input: "4193 with words"
Output: 4193
Explanation: Conversion stops at digit '3' as the next character is not a numerical digit.
Example4:
Input: "words and 987"
Output: 0
Explanation: The first non-whitespace character is 'w', which is not a numerical digit or a +/- sign. Therefore no valid conversion could be performed.
Example5:
Input: "-91283472332"
Output: -2147483648
Explanation: The number "-91283472332" is out of the range of a 32-bit signed integer.Thefore INT_MIN (−231) is returned.
解答
func myAtoi(str string) int {
if len(str) == 0 {
return 0
}
index := 0
for index < len(str) {
if str[index] == ' ' {
index++
} else {
break
}
}
sign := 1
if index < len(str) && (str[index] == '-' || str[index] == '+') {
if str[index] == '-' {
sign = -1
}
index++
}
// Build the result and check for overflow/underflow condition
minVal, maxVal, result := -1<<31, 1<<31-1, 0
for index < len(str) && str[index] >= '0' && str[index] <= '9' {
if result > maxVal/10 || result == maxVal/10 && int(str[index]-'0') > maxVal%10 {
if sign == 1 {
return maxVal
} else {
return minVal
}
}
result = result*10 + int(str[index]-'0')
index++
}
return result * sign
}func myAtoi(str string) int {
if len(str) == 0 {
return 0
}
idx, sign := 0, 1
for idx < len(str) && str[idx] == ' ' {
idx++
}
if idx < len(str) && (str[idx] == '-' || str[idx] == '+') {
if str[idx] == '-' {
sign = -1
}
idx++
}
result := 0
for idx < len(str) && isNumerical(str[idx]) {
n := int(str[idx] - '0')
if sign == 1 && result > (2147483647-n)/10 {
return 2147483647
}
if sign == -1 && -result < (-2147483648+n)/10 {
return -2147483648
}
result = result*10 + n
idx++
}
return result * sign
}
func isNumerical(b byte) bool {
return b >= '0' && b <= '9'
}本周出差，中台技术方案，从客户的需求来看，整个项目需求范围还不明确，我们自己提出的中台方案，其实客户已经有相应的平台来支撑。我们需要进一步细化需求，研究客户的微服务开发流程平台。