How to count how many substrings you have in a C string?

Question

https://www.urionlinejudge.com.br/judge/pt/problems/view/2126

This exercise I thought better read as string or not...

#include <stdio.h>

int main(void) {
char N1,quantidadesdeN1;

while(scanf("%s",&N1)!=EOF)
   {
     scanf("%s",&quantidadesdeN1);

     /*Como faço pra ver quantos N1 tem na variável quantidadesdeN1 com strcmp ?No strcmp tem jeito de pegar apenas partes da quantidadedeN1? Se caso não for possível resolver no strcmp tem outro jeito de resolver ?
     */
   }
return 0;
} 

Answer 1

You can use the function strstr(), this function checks the existence of a substring in a string, then just count the number of characters it has in the substring comparing to the string, or also the function strncmp()

If to check only from the beginning, Ex:

112
1125468

In this case you can cycle and traverse character by character, if different give a break and concludes that it is not Subsequence

It will also be necessary to allocate memory of 10^10 and 10^32 in the 2 strings, as required by the exercise.

Code:

#include <stdio.h>
#include <string.h>

int main(void)
{
    char N1[100], N2[100];
    int count=0, x=0;

    scanf(" %s",N1);
    scanf(" %s", N2);
    do
    {
        if(!strncmp(N2+x, N1, strlen(N1)))
        {
            count++;
            printf("N1 e´ uma substring de N2\n");
            printf("Qtd.Subsequencias %d\n", count);
            x+=strlen(N1);
        }
        else
            x+=1;
    }    while(x<strlen(N2));

}

I think that’s what you want to do, obviously we have to print the cycle, but it’s just one example

STDIN

12
123123123123

STDOUT

N1 e´ uma substring de N2
Qtd.Subsequencias 4

As we can see, in the last iteration Qtd.Subsequences is equal to 4. In this case the fastest way would be to use the function strncmp()

Answer 2

in the library you have a function called strncmp(str1, str2, numero_de_casas)

str1 => variable 1 str2 => variable 2 numero_de_casas => you put how many houses you want for comparison.

Place the function in a loop of repetition, which modifies the initial position of str2, a counting variable for the times that were found to str1, and finally a variable for first position

https://www.tutorialspoint.com/c_standard_library/c_function_strncmp.htm