C Multiple Input in One Line

Question

I am solving Problem 'Red Light Green Light' with code 'DOLL' on Code chef.

Code Chef: Red Light Green Light

In this Problem, I need to take N inputs in one line. I tried using scanf() but to no avail, It didn't worked. It was talking N inputs in N line which isn't what I want. I tried using fgets and strtok. But There was some error coming which I am not understanding. So How can I do it?

void main(){
    int T,N,K,sum_N=0;
    int test_arr[N];
    char name;
    char *token;
    scanf("%d",&T);
    if(T<0||T>100000) printf("Wrong Input Cases");  // Condition Checking for T
    if(sum_N>500000) printf("Exceeded Sum");    //Condition Checking for sum of N
    while(T--){
        scanf("%d %d",&N,&K);
        if((N||K)<0||(N||K)>100000) printf("Wrong Values"); //Conditon Checking for N and K
        // Here N Input in one Line are taken
        fgets(name,sizeof(name),stdin);
        token = strtok(name," ");
        for(int i=0;i<N;i++){
            test_arr[i] = *(token+i);
        }

        int ctr=0;
        for(int i=0;i<N;i++){
            if(test_arr[i]>K) ctr++;
        }
        printf("%d",ctr);
    }
}

Answer 1

You need to ask yourself a couple of questions:

• do you need to check for "invalid" input, and reject cases where the input is split over multiple lines.
• do you need to read all the numbers on a line of input WITHOUT knowing before hand how many there are supposed to be.

If the answer to both of those is no, there's no reason to check or care about what is on one line vs what is on another. Just use scanf to read numbers and don't worry about spacing or what is on which line.

scanf("%d", &test_cases);   // number of test cases
for (int i = 0; i < test_cases; ++i) {
    scanf("%d%d", &N, &height);  // number of values and boundary height
    int val[N];
    for (j = 0; j < N; ++j)
        scanf("%d", &val[j]);

Note that there are never any spaces or newlines in the scanf format strings. You don't need them, and they might cause confusion. You just read numbers. If you're paranoid, you can check the return value of scanf -- it should always be the number of items read (1, 2, or 1 in the 3 calls above), but if it is not, the only useful thing you can do is print an error message and exit.

If you do need to care about the newlines (most commonly because you don't know how many numbers will be on a line), use fgets + sscanf:

char buffer[MAXLINE];  // buffer big enough for the largest line
int vals[MAXVALS];     // array large enough for the maximum number of vals
char *p = fgets(buffer, sizeof(buffer));    // read a line
int N = 0, len;
while (N < MAXVALS && sscanf(p, "%d%n", &vals[N], &len) == 1) {
    p += len;
    ++N; }

Answer 2

Change char name; to char name[1024]; or something similar. char name; is not a string but a single character. fgets and strtok is looking for a pointer to a string but getting a character variable.