Converting a string into an int array

I would suggest you to use strtol or sscanf in a loop. That would make things easier for you.

Something like this:

char *c = "12 23 45 9";
int i[5];
sscanf(inputstring, "%d %d %d %d %d", &i[0], &i[1], &i[2], &i[3], &i[4]);

Sample example using atoi() which another option:

int main(int argc,char *argv[]){
    char y[10] = "0123456789";
    char x[3];
    int i;

    x[0] = y[8];
    x[1] = y[9];
    x[2] = '\0';

    i=atoi(x);
}

In ASCII the number symbols appear in the sequence as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. So all you have to do is this:

if (isdigit(input[y])) {
    digit[x++] = input[y++] - '0';

If the digit is '0', '0' - '0' = 0, if the digit is '1', '1' - '0' = 1, and so on.

See column 0x3 on the Wikipedia ASCII Quickref card.

You have to do few improve that we have to make sure array of int digit, array size should be same as how much input u type for eg.

input[12] : 12451'\0' <--- size of array of input is 12

Output :-

digit[12] : 124510000000

because remaining array size is unused so we have to make sure how input much u type it will be size of digit array

int main(void) {
  int x = 0;
  int y = 0 
  char input[12] = {0};


  scanf("%s", &input[0]);
  int ch_len = strlen(input)/sizeof(char);
  int digit[ch_len];    
  fflush(stdin);

  while (input[y] != '\0') {
      if (isdigit(input[y])) {
          digit[x++] = input[y++]-'0';
          count++;
      }
      else y++;
  }
}

This is my solution to parse all digits that can be mixed with other characters.

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

uint8_t atoia(char *src, int *dst, int len){
  // This function convert char array with digits into ints array.
  // In addition return amount of digits that was able to find in *src.
  // If more digits is in *src then max size of *dst, then zero is returned and 
  // *dst is zeroed.
  uint8_t k=0;
  uint8_t x=0;
  dst[x] = 0;
  while(*src++){
    if (*src >= '0' && *src <= '9'){
      if (x > len-1){
        memset(dst, 0, len*sizeof(uint8_t));
        return 0;
      }
      dst[x] = dst[x]*10 + *src - '0';
      k = 1;
    } else if (k>0){
      x++;
      dst[x] = 0;
      k = 0;
    }
  }
  return x;
}

int main(void){
  printf("Hello :)\n");
  char *buf = "This is mixed string 3 0 12 233 18 100 321 and 231 123345";
  int k=0;
  int dst[9]={0};

  k = atoia(buf, dst, 9);
  while(k--){
    printf("Number: %d: %d\n", k, dst[k]);
  }
  return 0;
}

Result:

Hello :)
Number: 8: 123345
Number: 7: 231
Number: 6: 321
Number: 5: 100
Number: 4: 18
Number: 3: 233
Number: 2: 12
Number: 1: 0
Number: 0: 3