Think I have an integer array like this:
a[0]=60; a[1]=321; a[2]=5;
now I want to convert the whole of this array into an integer number, for example int b become 603215 after running the code.
How to do it?
6 Answers
Use a std::stringstream:
#include <iostream>
#include <sstream>
int main() {
std::stringstream ss;
int arr[] = {60, 321, 5};
for (unsigned i = 0; i < sizeof arr / sizeof arr [0]; ++i)
ss << arr [i];
int result;
ss >> result;
std::cout << result; //603215
}
Note that in C++11 that mildly ugly loop can be replaced with this:
for (int i : arr)
ss << i;
Also, seeing as how there is a good possibility of overflow, the string form of the number can be accessed with ss.str(). To get around overflow, it might be easier working with that than trying to cram it into an integer. Negative values should be taken into consideration, too, as this will only work (and make sense) if the first value is negative.
Comments
int a[] = {60, 321, 5};
int finalNumber = 0;
for (int i = 0; i < a.length; i++) {
int num = a[i];
if (num != 0) {
while (num > 0) {
finalNumber *= 10;
num /= 10;
}
finalNumber += a[i];
} else {
finalNumber *= 10;
}
}
finalNumber has a result: 603215
6 Comments
Qaz
Just a couple of other things, the first being a Java->C++ one: 1. Arrays aren't classes in C++, and don't have a
length member. It's typically better to use std::vector instead, as it offers the functionality. 2. a should be arr.
Inside Man
@Kalai Thank you too, Nice and Smart Answer :))
Inside Man
@Kalai your code has a problem, think a[0]=50; a[1]=1; a[2]=0; then the result should be 5010, but your code will skip 0 and will show 501.
Kalai Selvan Ravi
@Stranger Thanks for your comment. You are having good analysing power. I have edited the code. Now, it will work.
Inside Man
@Kalai it is not working yet!!! use int a[] = {60, 321, 0}; as the first line and you will get no answer at all !!!
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Concat all the numbers as a string and then convert that to number
#include <string>
int b = std::stoi("603215");
1 Comment
Qaz
I know the question isn't too specific, but I would imagine the array elements can be arbitrary (to the point where it doesn't overflow the integer). Hardcoding a string value won't get around that. The function is a good alternative start (assuming you have C++11) to the stringstream, though.
This algorithm will work:
- Convert all the integer values of array into string using for loop.
- Append all the string values now to one string from index 0 to length of array.
- Change that string into an integer again.
1 Comment
Qaz
I made your algorithm easier to follow when reading it. FFR, there's a numbered list button at the top of the editing space.
Iterate the array and convert the values into string. Then concatenate all of them and convert back to integer.
#include <string>
int a[] = {60, 321, 5};
std::string num = "";
for(auto val : a)
num += a;
int b = std::stoi(num);
Comments
Array to Integer conversion
Number should be stored in opposite way
for(int i=0;i<d;i++)
{
ans += num[i]*pow(10,i);
}
stringstreamsolution seems simpler.