#include<stdio.h>
int main(){
  int n1,n2,x,y;
  printf("\nEnter two numbers:");
  scanf("%d %d",&n1,&n2);
  x=n1,y=n2;
  while(n1!=n2){
      if(n1>n2)
           n1=n1-n2;
      else
      n2=n2-n1;
  }
  printf("L.C.M=%d",x*y/n1);
  return 0;
}
Alternate Solution:
#include<stdio.h>

int lcm(int,int);

int main(){
    int a,b,l;

    printf("Enter any two positive integers ");
    scanf("%d%d",&a,&b);
 
    if(a>b)
         l = lcm(a,b);
    else
         l = lcm(b,a);
   
    printf("LCM of two integers is %d",l);

    return 0;
}

int lcm(int a,int b){
  
    int temp = a;

    while(1){
         if(temp % b == 0 && temp % a == 0)
             break;
         temp++;
    }

   return temp;
}

#include<stdio.h>

int lcm(int,int);

int main(){

   
    int a,b=1;
    printf("Enter positive integers. To quit press zero.");

    while(1){
         scanf("%d",&a);
         if(a<1)
             break;
         else if(a>b)
             b = lcm(a,b);
         else
             b = lcm(b,a);
    }

    printf("LCM is %d",b);

    return 0;
}

int lcm(int a,int b){
 
    int temp = a;

    while(1){
         if(temp % b == 0 && temp % a == 0)
             break;
         temp++;
    }

    return temp;
}

#include<stdio.h>
 
int main(){

    int x,y,m,i;

    printf("Insert any two number: ");

    scanf("%d%d",&x,&y);
    if(x>y)
         m=y;
    else
         m=x;

    for(i=m;i>=1;i--){
         if(x%i==0&&y%i==0){
             printf("\nHCF of two number is : %d",i) ;
             break;
         }
    }
    return 0;
}
Alternate Solution:
#include<stdio.h>
int main(){
int n1,n2;
printf("\nEnter two numbers:");
scanf("%d %d",&n1,&n2);
while(n1!=n2){
if(n1>=n2-1)
n1=n1-n2;
else
n2=n2-n1;
}
printf("\nGCD=%d",n1);
return 0;
}

#include<stdio.h>
int main(){
    int x,y=-1;
    printf("Insert numbers. To exit insert zero: ");
   
    while(1){
         scanf("%d",&x);
         if(x<1)
             break;
         else if(y==-1)
             y=x;
         else if (x<y)
             y=gcd(x,y);
         else
             y=gcd(y,x);
    }

    printf("GCD is %d",y);
   
    return 0;
}

int gcd(int x,int y){
    int i;
    for(i=x;i>=1;i--){
         if(x%i==0&&y%i==0){
             break;
         }
    }
    return i;
}

#include<stdio.h>

int main(){

    int a=5,b=10;

    //process one
    a=b+a;
    b=a-b;
    a=a-b;
    printf("a= %d  b=  %d",a,b);

    //process two
    a=5;b=10;
    a=a+b-(b=a);
    printf("\na= %d  b=  %d",a,b);

    //process three
    a=5;b=10;
    a=a^b;
    b=a^b;
    a=b^a;
    printf("\na= %d  b=  %d",a,b);

    //process four
    a=5;b=10;
    a=b-~a-1;
    b=a+~b+1;
    a=a+~b+1;
    printf("\na= %d  b=  %d",a,b);

    //process five
    a=5,b=10;
    a=b+a,b=a-b,a=a-b;
    printf("\na= %d  b=  %d",a,b);

    return 0;
}