Find and output longest string word c++ - c++

Question

I'm pretty new to programming and recently started working with strings. In my mind, this idea should somewhat work, but I have no idea what's wrong.
So I go through the string, with simb++ (to find length of the word) and where++ (to find where in the string am I) until I find a space, where I compare with the longest word I've found so so far (temp) and if it's longer, I make it the longest and find starting point of the word (start). When the for(...) ends, I write the word in the last for()
#include <iostream>
#include <string>
using namespace std;
int main()
{
string sentence;
string longest="";
int simb=0;
int temp=0;
int where=0;
int start=0;
cout<<"Input sentence"<<endl;
getline(cin,sentence);
for(int i=0 ; i<sentence.size() ; i++)
{
if(sentence[i]!=' ')
{
simb++;
where++;
}
if(sentence[i]==' ')
{
if(simb>temp)
{
where++;
simb++;
start=where-simb;
temp=simb;
}
simb=0;
}
}
for(int m=start ; m<=temp ; m++)
{
longest=longest+sentence[m];
}
cout<<"longest sentence"<<longest<<endl;
return 0;
}

Answer 1

There are a number of issues in your code:
if simb<=temp you don't increment where, you can just remove where completely and use i instead.
incrementing simb before calculating start results in start being 1 less than it should be
you don't check the length of last word in the string (assuming the string doesn't end with whitespace)
your final for loop goes from start to temp but should go from start to start + temp
Fixing these issues gives:
#include <iostream>
#include <string>
using namespace std;
int main()
{
string sentence;
int simb = 0;
int temp = 0;
int start = 0;
string sentence = "test test2 test 3 test 4 foo longest";
for (int i = 0; i <= sentence.size(); i++)
{
if (i != sentence.size() && sentence[i] != ' ')
{
simb++;
}
else
{
if (simb > temp)
{
start = i - simb;
temp = simb;
}
simb = 0;
}
}
string longest = "";
for (int m = start; m < start + temp; m++)
{
longest = longest + sentence[m];
}
cout << "longest sentence: '" << longest << "'\n";
return 0;
}
Note that using std::istringstream would be much simpler:
#include <iostream>
#include <string>
#include <sstream>
int main()
{
std::string sentence = "test test2 test 3 test 4 foo longest";
std::string longest;
std::stringstream ss(sentence);
std::string word;
while (ss >> word)
{
if (word.length() > longest.length())
{
longest = word;
}
}
std::cout << "longest sentence: '" << longest << "'\n";
return 0;
}

Answer 2

You can try this:
1.first locate where the spaces are.
2.calculate the gap between the two consequent words/strings.
3.find the word which has the maximum gap.
4.the world which has the maximum gap will be the longest one.
It's not c++ specific you can try this with any language.
Here is the c++ example:
#include <iostream>
#include <string>
using namespace std;
int main(){
//to get the user input
cout<<"Enter a sentence:"<<endl;
string s;
getline(cin,s);
// here the old value refers to the last index having space
// gap is the difference betweeen latest index having space and the old value
// max stores the maximum gap
int old=0;
int max=0;
int gap=0;
//these two values store the starting and ending index of longest string
int startIndex;
int endIndex;
// This for loop determines the maximum gap and calculates the starting
// and ending index of the longest word.
for(int i=0;i<s.size();i++){
if(isspace(s[i])|| i==s.size()){
if((i-old)>gap){
max=(i-old);
startIndex=i-max;
endIndex=i;}
gap=(i-old);
old=i+1;}
}
cout<<"longest string in the sentence is:";
//here we are using the determined starting and ending indices to print the longest word
for(int i=startIndex;i<=endIndex;i++){
cout<<s[i];
}
return 0;
}