75 lines
1.8 KiB
C++
75 lines
1.8 KiB
C++
#include <bits/stdc++.h>
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using namespace std;
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class Solution {
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public:
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void removeWhitespace(string &s) {
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int i = 0;
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while (i < s.length() && s[i] == ' ') i++;
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s = s.substr(i);
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}
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void conversion(string &s) {
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int i = 0;
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while (i < s.length() && s[i] == '0') i++;
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s = s.substr(i);
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i = 0;
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while (i < s.length() && s[i] >= '0' && s[i] <= '9') i++;
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s = s.substr(0, i);
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}
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bool isLessThan(string a, string b) {
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bool aIsNeg = false, bIsNeg = false;
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if (a[0] == '-') {
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aIsNeg = true;
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a = a.substr(1);
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}
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if (b[0] == '-') {
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bIsNeg = true;
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b = b.substr(1);
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}
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bool aIsPos = !aIsNeg, bIsPos = !bIsNeg;
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if (aIsNeg && bIsPos) return true;
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if (aIsPos && bIsNeg) return false;
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if (a.length() < b.length()) return aIsPos;
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if (a.length() > b.length()) return aIsNeg;
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for (int i = 0; i < a.length(); i++) {
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if (a[i] < b[i]) return aIsPos;
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if (a[i] > b[i]) return aIsNeg;
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}
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return false;
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}
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int myAtoi(string s) {
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// step 1: ignore whitespace
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removeWhitespace(s);
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if (s.length() == 0) return 0;
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// step 2: signedness
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bool isNeg = false;
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if (s[0] == '+') {
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s = s.substr(1);
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} else if (s[0] == '-') {
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s = s.substr(1);
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isNeg = true;
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}
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if (s.length() == 0) return 0;
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// step 3: conversion
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conversion(s);
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if (s.length() == 0) return 0;
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// step 4: rounding
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if (isNeg) s.insert(s.begin(), '-');
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if (isLessThan(s, to_string(INT32_MIN))) return INT32_MIN;
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if (isLessThan(to_string(INT32_MAX), s)) return INT32_MAX;
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return atoi(s.c_str());
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}
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}; |