75 lines
1.1 KiB
C
75 lines
1.1 KiB
C
#include <stdlib.h>
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#include <math.h>
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#include <stdio.h>
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double strtod(const char *nptr, char **endptr) {
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int sign = 1;
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if (*nptr == '-') {
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sign = -1;
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nptr++;
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}
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long long decimal_part = 0;
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while (*nptr && *nptr != '.') {
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if (*nptr < '0' || *nptr > '9') {
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break;
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}
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decimal_part *= 10LL;
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decimal_part += (long long)(*nptr - '0');
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nptr++;
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}
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double sub_part = 0;
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double multiplier = 0.1;
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if (*nptr == '.') {
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nptr++;
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while (*nptr) {
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if (*nptr < '0' || *nptr > '9') {
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break;
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}
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sub_part += multiplier * (*nptr - '0');
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multiplier *= 0.1;
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nptr++;
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}
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}
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double expn = (double)sign;
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if (*nptr == 'e' || *nptr == 'E') {
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nptr++;
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int exponent_sign = 1;
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if (*nptr == '+') {
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nptr++;
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} else if (*nptr == '-') {
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exponent_sign = -1;
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nptr++;
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}
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int exponent = 0;
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while (*nptr) {
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if (*nptr < '0' || *nptr > '9') {
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break;
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}
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exponent *= 10;
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exponent += (*nptr - '0');
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nptr++;
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}
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expn = pow(10.0,(double)(exponent * exponent_sign));
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}
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if (endptr) {
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*endptr = (char *)nptr;
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}
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double result = ((double)decimal_part + sub_part) * expn;
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return result;
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}
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