submission.c: In function ‘main’:
submission.c:4:2: error: initialization makes integer from pointer without a cast
  char W[100]={NULL};
  ^
submission.c:4:2: error: (near initialization for ‘W[0]’)
submission.c:13:17: error: comparison between pointer and integer
   while( W[i*2] != NULL ){
                 ^
submission.c:18:19: error: comparison between pointer and integer
   while( W[i*2+1] != NULL ){
                   ^
submission.c:7:2: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ^
submission.c:10:3: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%s", W);
   ^
~~~ c++

#include <stdio.h>

int main(){
    char W[100]={NULL};
    int i, n;

    scanf("%d", &n);

    while(n){
        scanf("%s", W);

        i=0;
        while( W[i*2] != NULL ){
            printf("%c", W[i*2]);
            i++;
        }
        i=0;
        while( W[i*2+1] != NULL ){
            printf("%c", W[i*2+1]);
            i++;
        }
        printf("\n");
        n--;
    }
    return 0;
}