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I have a large number that is initialized by a multidimensional string array and I need to do arithmetic operations on the elements of the array. I implemented the arithmetic operations with vectors but before that, I need to convert the multidimensional string array to a multidimensional vector.

C++
```<pre>
//Work out the first ten digits of the sum of the following one-hundred 50-digit numbers.
//The number is in the main()

#include <iostream>
#include <string>
#include <vector>

{
int carry=0;
if(left.size()==right.size())
{
for(int i=left.size()-1; i>=0; i--)
{
if(i==0)
{
left[i]=left[i]+right[i]+carry;
break;
}
left[i]=(left[i]+right[i]+carry);
carry=left[i]/10;
left[i]=left[i]%10;

}

}
if(left.size()>right.size())
{
int right_size=right.size()-1;
for(int i=left.size()-1; i>=left.size()-right.size(); i--)
{
left[i]=left[i]+right[right_size]+carry;
carry=left[i]/10;
left[i]=left[i]%10;
right_size--;
}

for(int i=right.size()-1; i>=0; i--)
{
left[i]=left[i]+carry;
}
}

if(right.size()>left.size())
{
int left_size=left.size()-1;
for(int i=right.size()-1; i>=right.size()-left.size(); i--)
{
right[i]=right[i]+left[left_size]+carry;
carry=right[i]/10;
right[i]=right[i]%10;
left_size--;
}
for(int i=left.size()-1; i>=0; i--)
{
right[i]=right[i]+carry;
}
}

}

///NEXT STEPS
//1)conversion of numbers matrix to int matrix is needed
std::vector<std::vector<int>>numbers(std::vector<std::vector<std::string>>str_numbers)
{
std::vector<std::string>left;

int left_row=0;
for(int col=0; col<50; col++)
{
std::string num=str_numbers[left_row][col];
left[col]=num-'0';
}

for(int row=0; row<100; row++)
{
for(int col=0; col<50; col++)
{

}
}
}

int main()
{
std::vector<int>left{1,4,5,7,2,1,5};
std::vector<int>right{2,2,1,4};

//75778645
std::string number[100]= {
{"37107287533902102798797998220837590246510135740250"},
{"46376937677490009712648124896970078050417018260538"},
{"74324986199524741059474233309513058123726617309629"},
{"91942213363574161572522430563301811072406154908250"},
{"23067588207539346171171980310421047513778063246676"},
{"89261670696623633820136378418383684178734361726757"},
{"28112879812849979408065481931592621691275889832738"},
{"44274228917432520321923589422876796487670272189318"},
{"47451445736001306439091167216856844588711603153276"},
{"70386486105843025439939619828917593665686757934951"},
{"62176457141856560629502157223196586755079324193331"},
{"64906352462741904929101432445813822663347944758178"},
{"92575867718337217661963751590579239728245598838407"},
{"58203565325359399008402633568948830189458628227828"},
{"80181199384826282014278194139940567587151170094390"},
{"35398664372827112653829987240784473053190104293586"},
{"86515506006295864861532075273371959191420517255829"},
{"71693888707715466499115593487603532921714970056938"},
{"54370070576826684624621495650076471787294438377604"},
{"53282654108756828443191190634694037855217779295145"},
{"36123272525000296071075082563815656710885258350721"},
{"45876576172410976447339110607218265236877223636045"},
{"17423706905851860660448207621209813287860733969412"},
{"81142660418086830619328460811191061556940512689692"},
{"51934325451728388641918047049293215058642563049483"},
{"62467221648435076201727918039944693004732956340691"},
{"15732444386908125794514089057706229429197107928209"},
{"55037687525678773091862540744969844508330393682126"},
{"18336384825330154686196124348767681297534375946515"},
{"80386287592878490201521685554828717201219257766954"},
{"78182833757993103614740356856449095527097864797581"},
{"16726320100436897842553539920931837441497806860984"},
{"48403098129077791799088218795327364475675590848030"},
{"87086987551392711854517078544161852424320693150332"},
{"59959406895756536782107074926966537676326235447210"},
{"69793950679652694742597709739166693763042633987085"},
{"41052684708299085211399427365734116182760315001271"},
{"65378607361501080857009149939512557028198746004375"},
{"35829035317434717326932123578154982629742552737307"},
{"94953759765105305946966067683156574377167401875275"},
{"88902802571733229619176668713819931811048770190271"},
{"25267680276078003013678680992525463401061632866526"},
{"36270218540497705585629946580636237993140746255962"},
{"24074486908231174977792365466257246923322810917141"},
{"91430288197103288597806669760892938638285025333403"},
{"34413065578016127815921815005561868836468420090470"},
{"23053081172816430487623791969842487255036638784583"},
{"11487696932154902810424020138335124462181441773470"},
{"63783299490636259666498587618221225225512486764533"},
{"67720186971698544312419572409913959008952310058822"},
{"95548255300263520781532296796249481641953868218774"},
{"76085327132285723110424803456124867697064507995236"},
{"37774242535411291684276865538926205024910326572967"},
{"23701913275725675285653248258265463092207058596522"},
{"29798860272258331913126375147341994889534765745501"},
{"18495701454879288984856827726077713721403798879715"},
{"38298203783031473527721580348144513491373226651381"},
{"34829543829199918180278916522431027392251122869539"},
{"40957953066405232632538044100059654939159879593635"},
{"29746152185502371307642255121183693803580388584903"},
{"41698116222072977186158236678424689157993532961922"},
{"62467957194401269043877107275048102390895523597457"},
{"23189706772547915061505504953922979530901129967519"},
{"86188088225875314529584099251203829009407770775672"},
{"11306739708304724483816533873502340845647058077308"},
{"82959174767140363198008187129011875491310547126581"},
{"97623331044818386269515456334926366572897563400500"},
{"42846280183517070527831839425882145521227251250327"},
{"55121603546981200581762165212827652751691296897789"},
{"32238195734329339946437501907836945765883352399886"},
{"75506164965184775180738168837861091527357929701337"},
{"62177842752192623401942399639168044983993173312731"},
{"32924185707147349566916674687634660915035914677504"},
{"99518671430235219628894890102423325116913619626622"},
{"73267460800591547471830798392868535206946944540724"},
{"76841822524674417161514036427982273348055556214818"},
{"97142617910342598647204516893989422179826088076852"},
{"87783646182799346313767754307809363333018982642090"},
{"10848802521674670883215120185883543223812876952786"},
{"71329612474782464538636993009049310363619763878039"},
{"62184073572399794223406235393808339651327408011116"},
{"66627891981488087797941876876144230030984490851411"},
{"60661826293682836764744779239180335110989069790714"},
{"85786944089552990653640447425576083659976645795096"},
{"66024396409905389607120198219976047599490197230297"},
{"64913982680032973156037120041377903785566085089252"},
{"16730939319872750275468906903707539413042652315011"},
{"94809377245048795150954100921645863754710598436791"},
{"78639167021187492431995700641917969777599028300699"},
{"15368713711936614952811305876380278410754449733078"},
{"40789923115535562561142322423255033685442488917353"},
{"44889911501440648020369068063960672322193204149535"},
{"41503128880339536053299340368006977710650566631954"},
{"81234880673210146739058568557934581403627822703280"},
{"82616570773948327592232845941706525094512325230608"},
{"22918802058777319719839450180888072429661980811197"},
{"77158542502016545090413245809786882778948721859617"},
{"72107838435069186155435662884062257473692284509516"},
{"20849603980134001723930671666823555245252804609722"},
{"53503534226472524250874054075591789781264330331690"}

};

}```

What I have tried:

I have tried to do it like this: num_array[row][col]=string_vec[row][col]-'0';
it gives a compiler error
Posted
Updated 29-Aug-18 5:16am
v2
[no name] 29-Aug-18 0:47am
This is not a very clear question. Converting a string to an int is easy to find using Google. Converting Strings to Numbers in C/C++ - GeeksforGeeks[^] Show the code you are using.
Manish K. Agarwal 29-Aug-18 3:59am
pls provide some sample input and expected output

## Solution 2

You may use the istringstream[^] class to perform the string to number conversion. E.g.
C++
```#include <iostream>
#include <sstream>
#include <vector>

using namespace std;

int main()
{
// the bidimensional vector of strings (string representation of integers)
vector < vector < string > > sv { { "10", "11", "12", "13" }, { "-1", "+1", "0", "2" }};

vector < vector < int > > iv; // the bidimensional vector of integers we have to fill

// fill the vector of integers
for ( const auto & row : sv)
{
iv.push_back( vector <int>() );
for ( const auto & v : row )
{ // convert string to integer using an instance of the 'istringstream class'
istringstream iss(v);
int i;
iss >> i;
iv.back().push_back(i);
}
}

// perform a simple operation on numeric values, let's double all the integers
for (auto & row : iv)
for (auto & x : row) x *= 2;

// report new values
for (const auto & row : iv)
{
for (const auto & x : row)
cout << x << " ";
cout << endl;
}
}```

Member 13277493 29-Aug-18 10:17am
thanks!
CPallini 29-Aug-18 10:29am
You are welcome.

## Solution 1

If you have stored numbers as strings in the array you must convert the in the correct manner. Use the function stod from the string class.

What you have done is a hack to convert a single char to a single number, which is working only for numbers from 0 to 9. So it is better to really understand what some code is doing, and not understanding code is very dangerous. :-O