How to extract integers from array of strings in C++ - c++

Question

Given an array of the form
char* timePeriod= {"6AM#8AM","11AM#1PM","7AM#3PM","7AM#10AM","10AM#12PM"};
how can I extract the start and end time in integer arrays of following form:
start_time={6,11,7,7,10}
end_time={8,1,3,10,12}

Answer 1

You can use "sscanf" to do so. And don't forget to mark it as useful :)
#include <stdio.h>
int main()
{
int a,b,i;
int start_time[5], end_time[5];
char *t[5] = {"6AM#8AM","11AM#1PM","7AM#3PM","7AM#10AM","10AM#12PM"};
char *(*ptr)[5] = &t;
for(i=0;i<5;i++)
{
sscanf((*ptr)[i], "%d%*[AP]M#%d%*[AP]M", &a, &b);
start_time[i]=a;
end_time[i]=b;
}
printf("Starting time : ");
for(i=0;i<5;i++)
{
printf("%d ",start_time[i]);
}
printf("\nEnding time : ");
for(i=0;i<5;i++)
{
printf("%d ",end_time[i]);
}
return 0;
}
OUTPUT:
Starting time : 6 11 7 7 10
Ending time : 8 1 3 10 12

Answer 2

A pretty simple way would be to use strtok to split the string on the #, then use atoi on each piece. It will stop once it sees a non-numeric value.

Answer 3

sscanf is capable of doing this, although I don't think it's a very good way. look at here for details
#include <stdio.h>
int main() {
const char* t = "6PM#8AM";
int a, b;
sscanf(t, "%d%*[AP]M#%d%*[AP]M", &a, &b);
printf("%d %d\n", a, b);
return 0;
}
or you can regex in C++11
#include <iostream>
#include <regex>
#include <string>
using namespace std;
int main() {
string t("6PM#8AM");
smatch match;
regex re("([[:digit:]])+[AP]M#([[:digit:]])+[AP]M");
if (regex_match(t, match, re)) {
cout << match[1].str() << " " << match[2].str() << '\n';
}
return 0;
}

Answer 4

Note: the following solution makes a few very specific assumptions about your dataset (if these are not the case, you may prefer using a regex).
The string will always start with integers
The endtimes will always either be in the 4th or 5th index of your string
Zero is not a valid time
#include <iostream>
#include <string>
int main() {
std::string timePeriod[5] = {"6AM#8AM","11AM#1PM","7AM#3PM","7AM#10AM","10AM#12PM"};
int startTimes[5] = {0,0,0,0,0};
int endTimes[5] = {0,0,0,0,0};
for(int i=0;i<5;i++) {
std::string s = timePeriod[i];
startTimes[i] = atoi(s.c_str()); // Convert first number to integer
endTimes[i] = atoi(s.substr(4).c_str()); // Convert 2nd numbers to integer
if(endTimes[i] == 0) // If zero
endTimes[i] = atoi(s.substr(5).c_str()); // Get the 5th index instead
std::cout << "Start: " << startTimes[i] << "\t End: " << endTimes[i] << std::endl;
}
}
The lack of leading zeros makes it a bit trickier, but ultimately - it can be quickly solved using substrings (assuming also you don't mind changing the char* into a std::string).