在 C 中进行数组输入后程序不继续

Question

#include<stdio.h>
int main(){
    printf("Enter the size of array: ");
    int n,a[n],element;
    scanf("%d", &n);
    printf("Enter the elements of array in ascending order\n");
    for(int i=0; i<n; i++){
        scanf("%d ", &a[i]);
    }
    printf("Enter the element to be searched: ");
    scanf("%d", &element);
    int low = 0;
    int high = n-1;
    int mid = (low+high)/2;
    int flag = 0;
    while(low<=high){
        if(a[mid]==element){
            flag =1;
            break;
        }
        if(a[mid]<element){
            low = mid + 1;
        }
        else{
            high = mid -1;
        }
    }
    if(flag){
        printf("%d found", element);
    }
    else{
        printf("Not found");
    }
    return 0;
}

When I run the code, I am only able to enter the elements of array and thus the program does not proceed further. What's wrong with the code?

Answer 1

int n,a[n],element;

Is equivalent of saying

int n;
int a[n];
int element;

Notice something? You're declaring an array of variable size with an uninitialized variable n . This leads to unexpected behaviour. Declare your array after the value of n has been set!

---

int n,element;
scanf("%d", &n);
int a[n];

Answer 2

On observing your code,

#include<stdio.h>
int main(){
    printf("Enter the size of array: ");
    int n,a[n],element;
    scanf("%d", &n);
    printf("Enter the elements of array in ascending order\n");
    for(int i=0; i<n; i++){
        scanf("%d", &a[i]); // correction: here you had given space after %d...
    }
    printf("Enter the element to be searched: ");
    scanf("%d", &element);
    int low = 0;
    int high = n-1;
    int mid = (low+high)/2;
    int flag = 0;
    while(low<=high){
        if(a[mid]==element){
            flag =1;
            break;
        }
        if(a[mid]<element){
            low = mid + 1;
        }
        else{
            high = mid -1;
        }
    }
    if(flag){
        printf("%d found", element);
    }
    else{
        printf("Not found");
    }
    return 0;
}

you had given space scanf("%d ", &a[i]); after %d which should not be used, that's why your program is not proceeding after taking array input... I am assuming your binary search operation is correct and working fine...