10034 - Freckles

[codeworrior]

got AC..didnt commented out freopen and tht ws causing problem..

[sarowar_csecu]

i'm getting WA. i can't find out the cause. help please. thanks in advance.

Code: Select all

#include <cstdlib>
#include<stdio.h>
#include<math.h>

using namespace std;

int main() {

    int tc, n,i,j,k,count;
    float **co,**gm,*nr,*d,res=0;



    scanf("%d",&tc);
    while(tc--){
        scanf("%d",&n);
        count=1;

        co = new float*[(n + 1)*(3)];
        gm = new float*[(n + 2)*(n + 2)];
        for (i = 0; i <= n; i++) {
            co[i] = new float[2];
            gm[i] = new float[n + 1];
        }        

        while(count<=n){
            scanf("%f %f", &co[count][0],&co[count][1]);
            count++;
        }
        

        for(i=1;i<=n;i++){
            for(j=1;j<=n;j++){
                float x=co[i][0]-co[j][0];
                float y=co[i][1]-co[j][1];
                gm[i][j]=sqrt(x * x + y*y); //x*x+y*y;
            }
        }

        d=new float[n+1];
        nr=new float[n+1];
        
        for (i = 2; i <= n; i++) {
            nr[i] = 1;
            d[i] = gm[1][i];
        }

        count = 0;
        int vnear;
        float min;
        while (count != n - 1) {
            min = 9999;
            for (i = 2; i <= n; i++) {
                if (0 <= d[i] && d[i] < min) {
                    min = d[i];
                    vnear = i;
                }
            }
            d[vnear] = -1;
            res+=min;

            for (i = 2; i <= n; i++) {
                if (d[i] > gm[i][vnear]) {
                    d[i] = gm[i][vnear];
                    nr[i] = vnear;
                }
            }
            count++;
        }
        printf("%.2f\n" ,res);
        if(tc>0)
            printf("\n");

    }

    return 0;
}

[sohel]

- Have you looked at other discussions related to this problem?
- Don't create a new thread for a problem that already exists.
- Try to include the problem name as well in the subject name... instead of 10034 WA, you can use something like 10034 - Freckles.

[jenovano2sko]

Despite the fact that the first few posts suggest you need a newline after your last line, UVa has fixed it! Print a blank line *only* between test cases, otherwise you won't get an AC. However, terminating the last line is okay, i.e.

okay >> "0.00\n" << okay
WRONG >> "0.00\n\n" << WRONG

Also, if anybody is wondering, I had the cases of only one point, and I'm not sure if it makes a difference, but I also had a case if they entered 0 points to output 0.

Good luck!

[Chocolate]

Hello all, just want to ask - I still got WA for this problem

I think my algo is correct, I just compute the distance between each points and do Prim's algorithm to get the MST.
I'm just confused with the output scenario with that "print blank line" rules.
for this input:

Code: Select all

3

3
1.0 1.0
2.0 2.0
2.0 4.0
1
1.0 1.0
2
0.0 0.0
2.0 2.0

Is this the correct output?

Code: Select all

3.41

0.00

2.83

(with a single newline character at the end of output)

[sith]

Hello
I've got WA
I've used Kruskal's algorithm.
Here is my solution
It gives same result like a previous post.

Code: Select all

import java.io.*;
import java.util.*;

class Main {


    public static void main(String[] args) {

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));

        Scanner scanner = new Scanner(reader);
        try {

            int cases = scanner.nextInt();
            for (int i = 0; i < cases; i++) {
                int frickles = scanner.nextInt();

                double[][] vertexes = new double[frickles][2];
                List<Edge> edges = new ArrayList<Edge>();
                double previousX = scanner.nextDouble();
                double previousY = scanner.nextDouble();

                vertexes[0][0] = previousX;
                vertexes[0][1] = previousY;

                for (int j = 0; j < frickles - 1; j++) {
                    double x = scanner.nextDouble();
                    double y = scanner.nextDouble();
                    for (int k = 0; k <= j; k++) {
                        double[] vertex = vertexes[k];
                        edges.add(new Edge(j + 1, k, getLength(x, y, vertex[0], vertex[1])));
                    }
                    vertexes[j + 1][0] = x;
                    vertexes[j + 1][1] = y;
                }

                Collections.sort(edges);

                Set<Integer> visitedVertex = new HashSet<Integer>();
                double length = 0;
                for (Edge edge : edges) {
                    if (visitedVertex.contains(edge.start) && visitedVertex.contains(edge.end)) {
                        continue;
                    }
                    visitedVertex.add(edge.start);
                    visitedVertex.add(edge.end);
                    length += edge.length;
                    if (visitedVertex.size() == frickles) {
                        break;
                    }
                }
                writer.write(String.format("%.2f", length));
                if (i != cases - 1) {
                    writer.write("\n\n");
                }
            }
            writer.flush();
        } catch (IOException e) {

        }
    }

    private static double getLength(double x, double y, double previousX, double previousY) {

        double xLength = Math.abs(x - previousX);
        double yLength = Math.abs(y - previousY);


        return Math.sqrt(xLength * xLength + yLength * yLength);
    }

    static class Edge implements Comparable<Edge> {
        int start;
        int end;
        Double length;

        Edge(int start, int end, double length) {
            this.start = start;
            this.end = end;

            this.length = length;
        }

        @Override
        public String toString() {
            return "Edge{" +
                    "start=" + start +
                    ", end=" + end +
                    ", length=" + length +
                    '}';
        }
        public int compareTo(Edge o) {
            return length.compareTo(o.length);
        }
    }
}

[brianfry713]

You didn't property implement Kruskal's algorithm.
Input:

Code: Select all

1

4
1.0 1.0
1.0 2.0
10.0 10.0
10.0 11.0

Correct output 14.04

[shimul_kar]

#include<stdio.h>
#include<math.h>
int root(int v,int p[]){

while(p[v] != v)
{v = p[v];}

return v;
}

void union_ij(int i,int j,int p[]){
if(j > i)
p[j] = i;
else
p = j;
}
int main()
{
int test,n,o,l,i,j,flag;
flag=0;
scanf("%d",&test);
for(o=0;o<test;o++)
{
scanf("%d",&n);
printf("\n");
double x[n],y[n],gra[n][n],weight;;
for(l=0;l<n;l++)
{
scanf("%lf%lf",&x[l],&y[l]);
}
for(i=0;i<n;i++)
for(j=0;j<n;j++)
{
gra[j]=9999;
}
for(i=0;i<n-1;i++)
for(j=i+1;j<n;j++)
{
weight=sqrt(pow((x-x[j]),2)+pow((y-y[j]),2));
gra[j]=weight;
gra[j]=weight;
}
//kruskal algorithm
int count,p[n],u, v;
count = 0;
double sum,min;
sum = 0;
for(i = 0; i < n; i++)
{
p = i;
}
while(count < n)
{
min = 9999;
for(i = 0; i < n; i++)
{
for(j = 0;j < n; j++)
{

if(gra[j] < min)
{
min = gra[j];
u = i;
v = j;

}
}
}
if(min != 9999)
{
i = root(u, p);
j = root(v, p);
if (i != j)
{
sum += min;
union_ij(i,j,p);
}
gra[v] = gra[v] = 9999;

}
count++;
}
if (flag == 1)
printf("\n");
flag = 1;
printf("%0.2lf\n",sum);
}
return 0;
}

[brianfry713]

Input:

Code: Select all

2

3
1.0 1.0
2.0 2.0
2.0 4.0

3
1.0 1.0
2.0 2.0
2.0 4.0

Correct output:

Code: Select all

3.41

3.41

[Top Secret]

Why wa? I used Kruskal's Mst algo.. I think its presentation error..

Here is my code:

Code: Select all

AC.

While(1) Return Thanks.. :) ;

[lbv]

Why wa? I used Kruskal's Mst algo.. I think its presentation error..

• Check out the output from your program with the sample case from the problem statement: http://ideone.com/QwUIBZ. It's printing "nan". Chances are this is related to the fact that you don't initialize the sum variable inside your mst function, so it starts out with "garbage". Try to configure your compiler to show you all warnings; it can help you catch this type of bugs.
• I'd suggest you avoid the "float" data type and use "double" instead.
• Take the time to go through the previous messages in this forum thread. There's a couple of posts from Mar 11, 2004, for example, which contain useful test cases.

[Top Secret]

WOW!!!!!!!!!!!! You know magic!

I changed float to double & initialized sum = 0 & got AC!!!! Don't know how to thank you!

& I had tried each and every given test case in this forum. My code gave me the correct outputs for them. So I totally had no idea why I was getting WA.. But now I know...

Thanks again..

[Munchor]

Code: Select all

#include <stdio.h>
#include <string.h>
#include <vector>
#include <queue>
#include <utility>
#include <cmath>

using namespace std;

#define MAX 101

double freckles[MAX][2];
int u, v, cases;
double mst_cost;
vector<int> pset(1000);
priority_queue< pair< double, pair <double, double> > > edge_list;

double distance(double x1, double y1, double x2, double y2)
{
  return sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
}

void read_input()
{
  scanf("%d", &v);

  memset(freckles, 0, sizeof freckles);

  for (u = 0; u < v; u++)
  {
    scanf("%lf %lf", &freckles[u][0], &freckles[u][1]);

    if (u == 0) continue;
    
    edge_list.push(make_pair(-distance(freckles[u - 1][0], freckles[u - 1][1],
                                       freckles[u][0], freckles[u][1]),
                             make_pair(u, u - 1)));
  }

  edge_list.push(make_pair(-distance(freckles[v - 1][0], freckles[v - 1][1],
                                     freckles[0][0], freckles[0][1]),
                           make_pair(v - 1, 0)));
}

void init_set(int _size)
{
  pset.resize(_size);

  int i;
  for (i = 0; i < _size; i++)
  {
    pset[i] = i;
  }
}

double find_set(int i)
{
  if (pset[i] == i)
  {
    return i;
  }
  else
  {
    return pset[i] = find_set(pset[i]);
  }
}

void union_set(int i, int j)
{
  pset[find_set(i)] = find_set(j);
}

bool is_same_set(int i, int j)
{
  return find_set(i) == find_set(j);
}

int main()
{
  scanf("%d\n", &cases);
  int i;

  for (i = 0; i < cases; i++)
  {
    read_input();
    
    mst_cost = 0;
    init_set(v);
    while (!edge_list.empty())
    {
      pair< double, pair <double, double> > front = edge_list.top();
      edge_list.pop();

      if (!is_same_set(front.second.first, front.second.second))
      {
        mst_cost += (-front.first);
        union_set(front.second.first, front.second.second);
      }
    }

    if (i == cases - 1)
      printf("%0.2lf\n", mst_cost);
    else
      printf("%0.2lf\n\n", mst_cost);
  }

  return 0;
}

I have that code, and I get correct output for this input:

Code: Select all

9

3
4.0 2.0
2.0 2.0
1.0 1.0

3
1.0 1.0
2.0 2.0
3.0 3.0

3
1.0 1.0
2.0 2.0
2.0 4.0

2
1.0 1.0
2.0 2.0

2
-1.0 -1.0
1.0 -1.0

1
1.0 1.0

2
2.0 2.0
2.0 2.0

4
1.0 1.0
1.0 2.0
10.0 10.0
10.0 11.0

1
1.0 -1.0

Code: Select all

3.41

2.83

3.41

1.41

2.00

0.00

0.00

14.04

0.00

I got WA no idea why, I really have tried everything... My code is just a normal Kruskal MST algorithm with union sets.

[Munchor]

I found my error, I had to connect ALL dots with all other dots, I was missing some dots.

[triplemzim]

Nice problem... Got ac . I solved this using Prim's algorithm. BUT my runtime is very bad. Any suggestion about optimizing my code will be appreciated. Thanks.