40 lines
1.0 KiB
C++
40 lines
1.0 KiB
C++
#include "s0008_string_to_integer.hpp"
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// 当流程很复杂的时候，画流程图: https://share.sainnhe.dev/NQxx.png
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class S0008Automaton {
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string state = "start";
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unordered_map<string, vector<string>> table = {
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{"start", {"start", "signed", "in_number", "end"}},
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{"signed", {"end", "end", "in_number", "end"}},
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{"in_number", {"end", "end", "in_number", "end"}},
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{"end", {"end", "end", "end", "end"}}};
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int get_col(char c) {
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if (isspace(c)) return 0;
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if (c == '+' or c == '-') return 1;
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if (isdigit(c)) return 2;
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return 3;
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}
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public:
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int sign = 1;
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long long ans = 0;
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void get(char c) {
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state = table[state][get_col(c)];
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if (state == "in_number") {
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ans = ans * 10 + c - '0';
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ans = sign == 1 ? min(ans, (long long)INT_MAX)
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: min(ans, -(long long)INT_MIN);
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} else if (state == "signed")
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sign = c == '+' ? 1 : -1;
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}
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};
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int S0008::myAtoi(string str) {
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S0008Automaton automaton;
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for (char c : str) automaton.get(c);
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return automaton.sign * automaton.ans;
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}
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