Struct sort on QUEST5

[dew_drop]

Hi all, I need your help. To solve this problems, in my opinion, I need to use a struct. I've declared my struct like this

typedef struct
{
    int one;
    int two;
} arr;

and then I've two arrays

arr a[n], b[n];

I want to sort array a, i use this code

sort(a.one, a.one+n);

and it's still a mistake. could you help me, how to sort a stucture?

Thanks.

[leppyr64]

sort(a,a+n);

cplusplus.com/reference/algorithm/sort/
They don't include all of that extra information for nothing

Another thing that I might avoid is naming a type struct. struct is actually a reserved word. Your "typedef" could have simply been:

struct arr
{
  int one,two;
};

typedef is typically used to rename a class that has a cumbersome name, for example you might see people rename long long:

typedef long long LL;

Feel free to post any questions that you may have.

[dew_drop]

thanks for your answer.

Just now, I asked my Friend about this problem and he told me that he used the qsort and two dimension array, not a struct.

I tried to write a code once more.

#include <iostream>
#include <algorithm>
using namespace std;
int compare (const void * a, const void * b)
{
  return ( *(int*)a - *(int*)b );
}
int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {   int n;
        scanf("%d", &n);
        int nail, pos_nail, a[2][n];
        for (int i=0; i<n; i++)
            scanf("%d %d", &a[0][i], &a[1][i]);
        qsort(a, n, 2*sizeof(int), compare);
        pos_nail=a[1][0];
        nail=0;
        for(int j=0; j<n; j++)
        printf("a[%d]= %d b =%d\n", j, a[0][j], a[1][j]);
        for(int i=1; i<n; i++)
        {
            if(a[0][i]>=pos_nail)
            {
                nail++;
                pos_nail=a[1][i];
            }
        }
        printf("%d\n", nail);
    }
    return 0;
}

but it does not work yet.

actually, I want to sort the a[0][i], and the a[1][i] will follow the a[0][i] besause both of them are correspondence to one another.

can you help me how to sort this?
Thanks

[leppyr64]

sort, qsort, it really doesn't matter. As you've referenced the array it won't work, a[n][2] will work, you just need to move around the pointers in the a[n].

With a[n][2], element a[0] is a pointer to a 2 element integer array.

Personally, I would go back to using the struct, but I won't fault you for following your friend's advice.

[dew_drop]

actually, I wanna go back using the struct, but I still confuse about the syntax.
can you show me how to using it?

here is my code

#include <iostream>
#include <algorithm>
using namespace std;
typedef struct
{
    int one;
    int two;
} arr;
int main()
{   
    int t, nail;
    scanf("%d", &t);
    while (t--)
    {   
        int n; nail=0;
        scanf("%d", &n);
        arr a[n], b[n];
        for (int i=0; i<n; i++)
            scanf("%d %d", &a[i].one, &b[i].two);
        sort(a.one, a.one+n);
        for (int i=0; i<n-1; i++)   
            for (int j=i+1; j<n; j++)
                {
                    if(b[i].two>a[i].one) nail++;
                }
        if (nail==0) nail++;
     printf("%d\n", nail);              
    }
    return 0;
}

if you don't mind, I'll be happy if you want to make some correction on my code

[dew_drop]

actually, I wanna go back using the struct. but I still confuse how to declare the sort.

here is my previous code before using qsort

#include <iostream>
#include <algorithm>
using namespace std;
typedef struct
{
    int one;
    int two;
} arr;
int main()
{   
    int t, nail;
    scanf("%d", &t);
    while (t--)
    {   
        int n; nail=0;
        scanf("%d", &n);
        arr a[n], b[n];
        for (int i=0; i<n; i++)
            scanf("%d %d", &a[i].one, &b[i].two);
        sort(a.one, a.one+n);
        for (int i=0; i<n-1; i++)   
            for (int j=i+1; j<n; j++)
                {
                    if(b[i].two>a[i].one) nail++;
                }
        if (nail==0) nail++;
     printf("%d\n", nail);              
    }
    return 0;
}

If you don't mind, I'll be happy if you want to make some correction on my code. thaaaanks

[system]

struct test {
        int a;
        int b;
};
bool compare ( test m, test n )
{
        return ( m.a < n.a );
}
int main()
{       .........................
        test t[n];
        ............................
        sort( t, t+n, compare );
}

[dew_drop]

thanks vipul, but its still getting WA
for test case
the first coloumn is a, and the second one is b. a and b is correspondence to each other.

1 5
3 5
2 4

i want to sort a, and the result
1 5
2 4
3 5

but, when I run my code, the result become
1 5
2 5
3 4

here is my code, where is my fault?

#include <iostream>
#include <algorithm>
using namespace std;
struct arr
{
    int one;
    int two;
};
bool compare ( arr m, arr n )
    { return ( m.one < n.one );    }
int main()
{   
    int t, nail;
    scanf("%d", &t);
    while (t--)
    {   
        int n; nail=0;
        scanf("%d", &n);
        arr a[n], b[n];
        for (int i=0; i<n; i++)
            scanf("%d %d", &a[i].one, &b[i].two);
        sort(a, a+n, compare);
        printf("after short\n");
        for (int i=0; i<n; i++)
        printf("%d %d\n", a[i].one, b[i].two);
        for (int i=0; i<n-1; i++)   
            for (int j=i+1; j<n; j++)
                {
                    if(b[i].two>a[i].one) nail++;
                }
        if (nail==0) nail++;
     printf("%d\n", nail);              
    }
    return 0;
}

[leppyr64]

You're using the struct so you don't need a and b. Just use a.

scanf("%d %d", &a[i].one, &a[i].two);