atoi

请你来实现一个 atoi 函数，使其能将字符串转换成整数。 首先，该函数会根据需要丢弃无用的开头空格字符，直到寻找到第一个非空格的字符为止。 当我们寻找到的第一个非空字符为正或者负号时，则将该符号与之后面尽可能多的连续数字组合起来，作为该整数的正负号；假如第一个非空字符是数字，则直接将其与之后连续的数字字符组合起来，形成整数。 该字符串除了有效的整数部分之后也可能会存在多余的字符，这些字符可以被忽略，它们对于函数不应该造成影响。 注意：假如该字符串中的第一个非空格字符不是一个有效整数字符、字符串为空或字符串仅包含空白字符时，则你的函数不需要进行转换。 在任何情况下，若函数不能进行有效的转换时，请返回 0。 说明： 假设我们的环境只能存储 32 位大小的有符号整数，那么其数值范围为 [−231, 231 − 1]。如果数值超过这个范围，qing返回 INT_MAX (231 − 1) 或 INT_MIN (−231) 。 示例 1: 输入: "42" 输出: 42 示例 2: 输入: " -42" 输出: -42 解释: 第一个非空白字符为 '-', 它是一个负号。 我们尽可能将负号与后面所有连续出现的数字组合起来，最后得到 -42 。 示例 3: 输入: "4193 with words" 输出: 4193 解释: 转换截止于数字 '3' ，因为它的下一个字符不为数字。 示例 4:

In the C language where did they come up with the name atoi for converting a string to an integer? The only thing I can think of is Array To Integer for an acronym but that doesn't really make sense. It means Ascii to Integer. Likewise, you can have atol for Ascii to Long, atof for Ascii to Float, etc. A Google search for 'atoi "ascii to integer"' confirms this on several pages. I'm having trouble finding any official source on it... but in this listing of man pages from Third Edition Unix (1973) collected by Dennis Ritchie himself, it does contain the line: atoi(III): convert ASCII to integer

前期回顾 今天又刷了一波leetcode 配合博客与GitHub记录自己的解题之路 具体代码可以在GitHub中git clone下来自己提交 GitHub地址（持续更新，欢迎star） 前面的刷题详见博客 LeetCode0001.两数之和 LeetCode0002两数相加 LeetCode0003无重复字符的最长子串 leetcode0004寻找两个有序数组的中位数 LeetCode0005最长回文子串 leetcode0006Z 字形变换 LeetCode0007整数反转 题目描述 请你来实现一个 atoi 函数，使其能将字符串转换成整数。 首先，该函数会根据需要丢弃无用的开头空格字符，直到寻找到第一个非空格的字符为止。 当我们寻找到的第一个非空字符为正或者负号时，则将该符号与之后面尽可能多的连续数字组合起来，作为该整数的正负号；假如第一个非空字符是数字，则直接将其与之后连续的数字字符组合起来，形成整数。 该字符串除了有效的整数部分之后也可能会存在多余的字符，这些字符可以被忽略，它们对于函数不应该造成影响。 注意：假如该字符串中的第一个非空格字符不是一个有效整数字符、字符串为空或字符串仅包含空白字符时，则你的函数不需要进行转换。 在任何情况下，若函数不能进行有效的转换时，请返回 0。 python3解法 解法1 class Solution : def myAtoi (

What is the difference between atoi and stoi ? I know, std::string my_string = "123456789"; In order to convert that string to an integer, you’d have to do the following: const char* my_c_string = my_string.c_str(); int my_integer = atoi(my_c_string); C++11 offers a succinct replacement: std::string my_string = "123456789"; int my_integer = std::stoi(my_string); 1). Are there any other differences between the two? 2). Efficiency and performance wise which one is better? 3). Which is safer to use? Ali 1). Are there any other differences between the two? I find std::atoi() a horrible function:

I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi value is shown as 0, but I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array? Please correct me if I am wrong. atoi() converts a string representation of an integer into its value. It will not convert arbitrary characters into their decimal value. For instance: int main(void) { const char *string="12345";

gcc 4.4.4 c89 What is better to convert a string to an integer value. I have tried 2 different methods atoi and sscanf. Both work as expected. char digits[3] = "34"; int device_num = 0; if(sscanf(digits, "%d", &device_num) == EOF) { fprintf(stderr, "WARNING: Incorrect value for device\n"); return FALSE; } or using atoi device_num = atoi(digits); I was thinking that the sscanf would be better as you can check for errors. However, atoi doesn't doing any checking. R.. You have 3 choices: atoi This is probably the fastest if you're using it in performance-critical code, but it does no error