Program to check if a number is a prime

merge.c

@@ -0,0 +1,58 @@
+#include<stdio.h>
+
+int a[1000000];
+
+void merge(int low, int mid, int high){
+	int n1=mid-low+1;
+	int n2=high-mid;
+	int i,j,k;
+	int left[1000000],right[1000000];
+
+	for(i=0;i<n1;i++)
+		left[i]=a[low+i];
+	for(i=0;i<n2;i++)
+		right[i]=a[mid+1+i];
+	i=0,j=0,k=low;
+	while(i<n1 && j<n2){
+		if(left[i]<=right[j]){
+			a[k++]=left[i++];
+		}
+		else{
+			a[k++]=right[j++];
+		}
+	}
+	while(i<n1)
+		a[k++]=left[i++];
+	while(j<n2)
+		a[k++]=right[j++];
+}
+
+void sort(int low, int high){
+	int mid;
+	//mid = (low+high)/2;
+	if(low<high){
+		mid = (low+high)/2;
+		sort(low,mid);
+		sort(mid+1,high);
+		merge(low,mid,high);
+	}
+}
+
+int main(){
+	int n,len;
+	int i=0;
+	while(scanf("%d",&n)!=EOF){
+		a[i++]=n;
+	}
+	len=i;
+	//printf("%d\n",i);
+	//for(i=0;i<len;i++)
+	//	printf("%d ", a[i]);
+	//printf("\n");
+	sort(0,len-1);
+	for(i=0;i<len;i++){
+		printf("%d ",a[i]);
+	}
+	printf("\n");
+	return 0;
+}

prime checker.c

@@ -0,0 +1,25 @@
+#include<stdio.h>
+#include<math.h>
+
+int main(){
+	int num;
+
+	scanf("%d",&num);
+
+	int isPrime = 1;
+
+	int i;
+	for(i=2;i<=sqrt(num);i++){
+		if(num%i == 0){
+			isPrime = 0;
+			break;
+		}
+	}
+	if(isPrime && num > 1){
+		printf("The number is a prime.");
+	} else{
+		printf("The number is not a prime.");
+	}
+
+	return 0;
+}