No output from c loop-CodePudding

Recently I coded a program to choose k numbers from the string in order from left to right to print out the number that has k characters and the smallest that can be made from the string itself for example : Input : 3 89678982 Output: 672 Then my code didn't print at all!! Code :

#include<bits/stdc  .h>
using namespace std;
int k,j=0,i;
string s;
int main() {
    cin>>k>>s;
    for(int i=0;i<s.size();i  ) s[i]-=48;
    int the2=0;
    int Min=s[0];
    while(j<0) {
    for(i=the2;i<s.size();i  ) {
            if(Min>s[i]) 
            {
                Min=s[i];
                break;
            }
        }
        the2=i;
        Min=s[i 1];
        cout<<Min;
        j  ;
    }
}

Why did this happen and how do I fix it?

CodePudding user response：

For starters this condition of the while loop

while(j<0) {

evaluates to false at once because the variable j was initialized by 0.

int k,j=0,i;

Also this for loop

for(i=the2;i<s.size();i  ) {
        if(Min>s[i]) 
        {
            Min=s[i];
            break;
        }
    }

finds the first character that is less than Min initially equal to the value s[0]. But you need to find the minimal value of the string in the range [0, s.length() - k 1)

That is the program does do what is described in the assignment.

It seems you mean something like the following.

#include <iostream>
#include <string>
#include <iterator>
#include <algorithm>

int main()
{
    std::string s;
    size_t k = 0;

    std::cin >> k >> s;

    if (not ( s.size() < k ))
    {
        auto it = std::begin( s );

        for (size_t i = 0; i < k; i  )
        {
            it = std::min_element( it,
                     std::prev( std::end( s ), k - i - 1) );
            std::cout << *it  ;
        }

        std::cout << '\n';
    }
}

If to enter

3 89678982

then the output will be

If to use a for loop instead of calling the standard algorithm std::min_element then program can look the following way

#include <iostream>
#include <string>
#include <iterator>
#include <algorithm>

int main()
{
    std::string s;
    size_t k = 0;

    std::cin >> k >> s;

    if (not ( s.size() < k ))
    {
        std::string::size_type pos = 0;

        for (size_t i = 0; i < k; i  )
        {
            for (auto j = pos; j < s.size() - k   i   1; j  )
            {
                if (s[j] < s[pos]) pos = j;
            }

            std::cout << s[pos  ];
        }

        std::cout << '\n';
    }
}

CodePudding user response：

You don't print because j=0 so the while loop's condition (j<0) is false from the beginning. So it's body will not be executed at all. And your cout is inside that loop