coding-interviews/53.cpp at master · bodhiye/coding-interviews · GitHub

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#include <iostream>
#include <string>

using namespace std;

bool isNumeric(char *string) {
    int n = strlen(string);
    if (n == 0 || (n == 1 && (string[0] < '0' || string[0] > '9')))
        return false;
    bool sign = false, dec = false, hasE = false;
    for (int i = 0; i < n; i++) {
        if (string[i] == '+' || string[i] == '-') {
            if (!sign && i > 0 && string[i - 1] != 'e' && string[i - 1] != 'E')
                return false;
            if (sign && string[i - 1] != 'e' && string[i - 1] != 'E')
                return false;
            sign = true;
        } else if (string[i] == 'e' || string[i] == 'E') {
            if (i == 0 || i == n - 1)
                return false;
            if (hasE)
                return false;
            hasE = true;
        } else if (string[i] == '.') {
            if (hasE || dec || i == 0 || i == n - 1)
                return false;
            dec = true;
        } else if (string[i] < '0' || string[i] > '9')
            return false;
    }
    return true;
}

int main() {
    ios::sync_with_stdio(false);
    char a[101];
    cin >> a;
    cout << isNumeric(a);
    return 0;
}