Find 2nd largest element from stdin without using an array - c

Question

#include<stdio.h>
int main() {
int i, m1, m2, n, num;
puts("\n");
scanf("%d",&n);
for(i = 0; i < n; i++) {
scanf("%d", &num);
if(i == 0) {
num = m1 = m2;
}
if(num > m1) {
m2 = m1;
m1 = num;
} else if(num > m2) {
m2 = num;
}
}
return 0;
}
my stdin: -950 -588 -169 -187 -445 400 -1
I have to get stdout: -169 but its showing stdout: \n
Note: I want to solve this problem without arrays.

Answer 1

the statement:
num = m1 = m2;
is wrong and it does not cause the three variables to have the same value. You need to assign m1 and m2 to num. You are overwriting the variable that you previously had read. Change it to:
m1 = num;
m2 = num;
Then, print out the m2.
EDIT:
As others found out, the -1 states for end of your input. Adding simple if statement solves the problem and for your input -169 is the second largest element.
Full code:
#include<stdio.h>
int main(){
int i, m1, m2, n, num;
puts("\n");
scanf("%d",&n);
for(i=0;i<n;i++)
{
scanf("%d",&num);
if(i==0)
{
m1 = num;
m2 = num;
}
else if(num == -1) /* if -1 was read, then terminate the loop. */
{
break;
}
else if(num>m1)
{
m2 = m1;
m1 = num;
}
else if(num>m2)
{
m2=num;
}
}
printf("%d\n",m2);
return 0;
}
For input:
7
-950 -588 -169 -187 -445 400 -1
and current code output is -169.
Another EDIT:
Ok, your code is wrong because of the scanf for number of elements. In future It would be helpful if you were more clear about your problems. I hope that following code will work for you.
#include <stdio.h>
int main(void)
{
int curr, second, first;
scanf("%d", &curr);
second = curr;
first = curr;
while (1) {
scanf("%d", &curr);
if (curr == -1) {
break;
}
if (curr > first) {
second = first;
first = curr;
}
else if (curr > second) {
second = curr;
}
}
printf("%d\n",second);
return 0;
}

Answer 2

/* Program to find the second largest number without using array */
main()
{
int num,large=0,slarge=0,i=0;
clrscr();
printf("Enter the number:");
while(i<10)
{
scanf("%d",&num);
if(i==0)
{
large=num;
}
else if(num>large)
{
slarge=large;
large=num;
}
else if(num>slarge)
{
slarge=num;
}
i++;
}
printf("Large number:%d",large);
printf("\nSecond large=%d",slarge);
getch();
return 0;
}

Answer 3

The problem with your code is you are using m2 uninitialized. To correct the problem, set m2 to some reasonable negative number (like the smallest integer allowed). Here we are just using a negative number for example:
m2 = -1000000;
outout
argument [0]: -950
argument [1]: -588
argument [2]: -169
argument [3]: -445
argument [4]: 400
argument [5]: -1
m1: 400
m2: -1
Your code does what you intend. -1 is the second largest number (400 is the largest). If you want -169, then you want the 3rd largest. Remember:
ALWAYS INITIALIZE YOUR VARIABLES

Answer 4

here's a working and simpler version :
#include <stdio.h>
#include <limits.h>
int main(int argc , char** argv)
{
int m1 , m2 , rc = 1;
m1 = m2 = INT_MIN ;
while(rc)
{
scanf("%d" , &rc);
if(rc > m1)
m1 = rc;
else if(rc < m1 && rc > m2)
m2 = rc;
}
printf("%d\n" , m2);
}

Answer 5

/*Second largest elements in a given array*/
#include <stdio.h>
int SecondMax(int a[], int n) // n= array size
{
int max1, max2; //assume max1 as largest and max2 is second largest
max1= max2= a[0]; //Initialize first element of array
for(int i=0; i<n; i++)
{
if(a[i] > max1) //check each elements of array with max1
{
max2= max1;
max1= a[i];
}
else if(a[i] > max2)
max2= a[i];
}
return max2;
}
int main()
{
int a[10]={2, 54, 8, 9 ,12, 6, 3, 7, 32, -5};
printf("\nmax2= %d", SecondMax(a, 10)); //print return value
return 0;
}