Create combinations.c

Mathematical/combinations.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+long int factorial(long int n);
+
+long int calcomb(long int n,long int r);
+
+int main(){
+
+    long int n=0,r=0;
+
+    printf("This is a Program to calculate the combinations of r things out of n things\nEnter the value of n and r\n");
+
+    scanf("%ld%ld", &n, &r);
+
+    if(r>n){
+
+        printf("Wrong input detected\nGive input in the range 0<=r<=n\n");
+
+        return 0;
+    }
+
+    printf("The combinations of r things out of n things is\t%ld",calcomb(n,r));
+
+    return 0;
+}
+
+long int factorial(long int n){
+
+    if(n<=0){
+        return 1;
+    }
+
+    else{
+
+        return (n)*factorial(n-1);
+    }
+};
+
+long int calcomb(long int n,long int r){
+
+    return (factorial(n)/(factorial(r)*factorial(n-r)));
+};