# C++ hex2dec string function

```#include <iostream> #include <sstream> #include <cstdio>   using namespace std;   unsigned long long hex2dec(const string &input); unsigned long long hex2dec_c(const char*s, int length);   int main(int argc, char *argv[]) { string i1 = "FF"; string i2 = "7FFFFFFF"; string i3 = "FFFFFFFF"; string i4 = "1004CCB00";//if hex2dec returned int, this would overflow it   cout << i1 << "," << hex2dec(i1)<< "," << hex2dec_c(i1.c_str(),i1.length()) << endl; cout << i2 << "," << hex2dec(i2)<< "," << hex2dec_c(i2.c_str(),i2.length()) << endl; cout << i3 << "," << hex2dec(i3)<< "," << hex2dec_c(i3.c_str(),i3.length()) << endl; cout << i4 << "," << hex2dec(i4)<< "," << hex2dec_c(i4.c_str(),i4.length()) << endl;   return 0; }   unsigned long long hex2dec(const string &input) { unsigned long long n; stringstream ss; ss << hex << uppercase << input; //ss << hex << lowercase << input; ss >> n; return n; }   unsigned long long hex2dec_c(const char*s, int length) { unsigned long long n=0; for(int i=0,v=0; i<length && s[i]!='\0'; i++) { int v; if ('a' <= s[i] && s[i] <='f') { v=s[i]-97+10; } else if ('A' <= s[i] && s[i] <='F') { v=s[i]-65+10; } else if ('0' <= s[i] && s[i] <='9') { v=s[i]-48; } else break; n*=16; n+=v; } return n; }```
```FF,255,255 7FFFFFFF,2147483647,2147483647 FFFFFFFF,4294967295,4294967295 1004CCB00,4300000000,4300000000```
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