string-to-integer-atoi.rs

#![allow(dead_code, unused, unused_variables)]

fnmain(){
assert_eq!(42,Solution::my_atoi("42".to_string()));
assert_eq!(-42,Solution::my_atoi(" -42".to_string()));
assert_eq!(4193,Solution::my_atoi("4193 with words".to_string()));
assert_eq!(0,Solution::my_atoi("words and 987".to_string()));
assert_eq!(-2147483648,Solution::my_atoi("-91283472332".to_string()));
assert_eq!(0,Solution::my_atoi(" ++1".to_string()));
assert_eq!(2147483647,Solution::my_atoi("21474836460".to_string()));
assert_eq!(0,Solution::my_atoi("-+12".to_string()));
}

structSolution;

implSolution{
pubfnmy_atoi(s:String) -> i32{
// 丢弃无用的前导空格
let s = s.trim_start_matches(" ");
// 判断是否是字母开头或者.开头
if s.starts_with(char::is_alphabetic) || s.starts_with("."){
return0;
}

// 结果、是否为正数、是否溢出、是否开始计算
let(mut result,mut is_positive,mut is_overflow) = (0,true,false);

for(i, v)in s.bytes().enumerate(){
if i == 0{
if v == b'-'{
 is_positive = false;
}elseif v == b'+'{
 is_positive = true;
}else{
 result = (v - b'0')asi32;
}
}else{
if v < b'0' || v > b'9'{
break;
}

let s = result.overflowing_mul(10);
if s.1{
 is_overflow = true;
break;
}

let s = s.0.overflowing_add((v - b'0')asi32);
if s.1{
 is_overflow = true;
break;
}

 result = s.0;
}
}

if is_positive {
if is_overflow {
 std::i32::MAX
}else{
 result
}
}else{
if is_overflow {
 std::i32::MIN
}else{
 result * -1
}
}
}
}