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Copy pathP_65.cpp
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66 lines (63 loc) · 1.34 KB
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#include <bits/stdc++.h>
#define fast_io \
ios::sync_with_stdio(false); \
cin.tie(nullptr);
using namespace std;
bool isDecimal(string s) {
int dotIdx = -1;
bool sign = false;
for (int i = 0; i < s.length(); i++) {
char c = s[i];
if (c == '+' || c == '-') {
if (i > 0) {
return false;
}
sign = true;
} else if (c == '.') {
if (dotIdx != -1) {
return false;
}
dotIdx = i;
}
}
int l = dotIdx - (sign ? 1 : 0);
int r = s.length() - (dotIdx + 1);
return l > 0 || r > 0;
}
bool isInteger(string s) {
if (s.find('.') != string::npos) {
return false;
}
int digits = 0;
for (int i = 0; i < s.length(); i++) {
char c = s[i];
if (c == '+' || c == '-') {
if (i > 0) {
return false;
}
} else {
digits++;
}
}
return digits > 0;
}
bool isNumber(string s) {
int eIdx = -1;
for (int i = 0; i < s.length(); i++) {
char c = tolower(s[i]);
if (c == 'e') {
if (eIdx != -1) {
return false;
}
eIdx = i;
} else if ('a' <= c && c <= 'z') {
return false;
}
}
if (eIdx == -1) {
return s.find('.') != string::npos ? isDecimal(s) : isInteger(s);
}
string l = s.substr(0, eIdx);
string r = s.substr(eIdx + 1, s.length() - eIdx);
return isNumber(l) && isInteger(r);
}