//编写函数实现库函数atoi。把字符串转换成整形 #include <stdio.h> #include <string.h> int my_atoi(const char *src) { int flag=1; int sum=0; while (*src) { if (*src == ' ') src++; else if (*src == '+') { src++; flag = 1; } else if(*src == '-') { src++; flag = -1; } else if(*src >= '0'&&*src <= '9') { sum = sum * 10 + (*src - '0'); src++; } else { return 0; } } sum = sum*flag; return sum; } int main() { printf("%d ", my_atoi(" +12345")); printf("%d ", my_atoi(" -12345")); printf("%d ", my_atoi("+12345")); printf("%d ", my_atoi("-12345")); printf("%d ", my_atoi("123 45")); printf("%d ", my_atoi("234 5")); printf("%d ", my_atoi("")); printf("%d ", my_atoi("123ab")); return 0; }