10/21/12algorithm - create ancestor matrix for binary tree - Stack Overflow

1/2stackoverflow.com/questions/12664257/create-ancestor-matrix-for-binary-tree

jrouquie

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Sree Ram

36 1 5

1 Answer

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for the given binary tree we need to create a matrix a[7][7] satisfying the ancestor property like a[2][1]=1

since 1 is an ancestor of 2 ....

i solved it by using extra space an array ...the solution i came up is

int a[n][n]={0};

void updatematrix(int a[][n],struct node *root,int temp[],int index){

if(root == NULL)

return ;

int i;

for(i=0;i< index;i++)

a[root->data][temp[i]]=1;

temp[index]=root->data;

updatematrix(a,root->left,temp,index+1);

updatematrix(a,root->right,temp,index+1);

}

is there any mistake in my solution ? can we do this inplace ???(i mean without using the temp array )

algorithm tree

edited Sep 30 at 20:01 asked Sep 30 at 19:20

80% accept rate

Perhaps you should do something about your accept rate. – Ted Hopp Sep 30 at 19:23

@TedHopp i am new to this site ..can u pls say how to increase the accept rate ..? – Sree Ram Sep 30 at

19:25

I guess that in your code you need to replace the first occurence of arr by a, and replace the second

occurrence of arr by temp. – jrouquie Sep 30 at 19:50

@jrouquie yup ..thank you ..edited .. – Sree Ram Sep 30 at 19:53

Go to some of the questions that you've asked (click on your name to see your profile, which includes links to

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check mark next to the answer. This has several benefits: it lets others know that the question has been

answered; it also lets others know which answer worked; it gives +15 reputation bonus to the person who

provided the answer; it gives you +2 reputation bonus. – Ted Hopp Sep 30 at 19:59

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temp contains the path from root to current node, i.e. the set of nodes visited while walking down the

tree to arrive at the current node.

If you have a parent pointer in each node (but I guess not), you can follow those pointers and walk up

the tree to traverse the same set of nodes as temp. But this uses more memory.

create ancestor matrix for binary tree

10/21/12algorithm - create ancestor matrix for binary tree - Stack Overflow

2/2stackoverflow.com/questions/12664257/create-ancestor-matrix-for-binary-tree

jrouquie

1,862 4 12

You can also walk down the tree several times (pseudocode):

def updatematrix(a,node):

if node is null: return

walkDown(a.data,node.left)

walkDown(a.data,node.right)

updatematrix(a,node.left)

updatematrix(a,node.right)

def walkDown(data,node):

if node is null: return

a[node][data] = 1

walkDown(data,node.left)

walkDown(data,node.right)

Same complexity, but the pattern of memory access looks less cache friendly.

answered Oct 1 at 6:49

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