40 lines
1.0 KiB
C++
40 lines
1.0 KiB
C++
|
#include "s0008_string_to_integer.hpp"
|
||
|
|
|
||
|
|
// 当流程很复杂的时候，画流程图: https://paste.sainnhe.dev/NQxx.png
|
||
|
|
|
||
|
|
class Automaton {
|
||
|
|
string state = "start";
|
||
|
|
unordered_map<string, vector<string>> table = {
|
||
|
|
{"start", {"start", "signed", "in_number", "end"}},
|
||
|
|
{"signed", {"end", "end", "in_number", "end"}},
|
||
|
|
{"in_number", {"end", "end", "in_number", "end"}},
|
||
|
|
{"end", {"end", "end", "end", "end"}}};
|
||
|
|
|
||
|
|
int get_col(char c) {
|
||
|
|
if (isspace(c)) return 0;
|
||
|
|
if (c == '+' or c == '-') return 1;
|
||
|
|
if (isdigit(c)) return 2;
|
||
|
|
return 3;
|
||
|
|
}
|
||
|
|
|
||
|
|
public:
|
||
|
|
int sign = 1;
|
||
|
|
long long ans = 0;
|
||
|
|
|
||
|
|
void get(char c) {
|
||
|
|
state = table[state][get_col(c)];
|
||
|
|
if (state == "in_number") {
|
||
|
|
ans = ans * 10 + c - '0';
|
||
|
|
ans = sign == 1 ? min(ans, (long long)INT_MAX)
|
||
|
|
: min(ans, -(long long)INT_MIN);
|
||
|
|
} else if (state == "signed")
|
||
|
|
sign = c == '+' ? 1 : -1;
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
int Solution::myAtoi(string str) {
|
||
|
|
Automaton automaton;
|
||
|
|
for (char c : str) automaton.get(c);
|
||
|
|
return automaton.sign * automaton.ans;
|
||
|
|
}
|