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February 26, 2013 03:15
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c implementation of triplets problem on interview street [ first attempt , not at all optimized ]
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#include <stdio.h> | |
#include <string.h> | |
#include <math.h> | |
#include <stdlib.h> | |
struct node { | |
int data; | |
int frequency; | |
struct node* left; | |
struct node* right; | |
}; | |
struct node* getnode(int data, int frequency) { | |
struct node* newnode = (struct node*) malloc(sizeof(struct node)); | |
newnode->left = NULL; | |
newnode->right = NULL; | |
newnode->data = data; | |
if(frequency < 0) | |
newnode->frequency = 0; | |
else | |
newnode->frequency = frequency; | |
return newnode; | |
} | |
void insert(struct node* root, int new_data, int frequency) { | |
if(new_data > root->data) { | |
if(root->right) | |
insert(root->right, new_data, frequency); | |
else | |
root->right = getnode(new_data, frequency); | |
} | |
else if(new_data < root->data) { | |
if(root->left) | |
insert(root->left, new_data, frequency); | |
else | |
root->left = getnode(new_data, frequency); | |
} | |
else if(new_data == root->data) { | |
if(frequency < 0) | |
root->frequency = 0; | |
} | |
} | |
int getSum(struct node* root) { | |
if(!root) | |
return 0; | |
else { | |
return root->frequency + getSum(root->left) + getSum(root->right); | |
} | |
} | |
int main() { | |
int size, t; | |
int d[100000]; | |
int middle; | |
int frequency = 1; | |
int i, j, k, lower=0, higher=0, triplets=0; | |
int total_lower, total_higher; | |
scanf("%d", &size); | |
for(i = 0; i < size; i++) { | |
scanf("%d", &d[i]); | |
} | |
for(j = 1; j < size-1; j++) { | |
middle = abs(d[j]); | |
lower = 0; | |
higher = 0; | |
struct node* root_l = getnode(middle, 1); | |
frequency = 1; | |
for(i = 0 ; i < j; i++) { | |
insert(root_l, abs(d[i]), frequency); | |
} | |
struct node* root_h = getnode(middle, 1); | |
frequency = 1; | |
for(i = j+1 ; i < size; i++) { | |
if(d[i] == middle) { | |
frequency = -1; | |
continue; | |
} | |
insert(root_h, abs(d[i]), frequency); | |
} | |
lower = getSum(root_l->left); | |
higher = getSum(root_h->right); | |
triplets += lower * higher ; | |
} | |
printf("%d", triplets); | |
return 0; | |
} |
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