// P4 task
// Gialam Tran

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

#define PI 3.14159265358979323846

typedef struct groupData {
	int members;
	double theta;
} groupData;

// Function to swap two groups' angles
void exchange(groupData* array, int i, int j) {
	double temporary = array[i].theta;
	array[i].theta = array[j].theta;
	array[j].theta = temporary;
}

// Function to set a pivot for the quicksort algorithm
int setPivot(groupData* array, int start, int end) {
	double pivotValue = array[end].theta;
	int pivotIndex = (start - 1);
	for (int idx = start; idx <= end; idx++) {
		if (array[idx].theta < pivotValue) {
			pivotIndex++;
			exchange(array, pivotIndex, idx);
		}
	}
	exchange(array, pivotIndex + 1, end);
	return (pivotIndex + 1);
}

// The quicksort algorithm for sorting the groups by angle
void angleSort(groupData* array, int start, int end) {
	if (start < end) {
		int pivot = setPivot(array, start, end);
		angleSort(array, start, pivot - 1);
		angleSort(array, pivot + 1, end);
	}
}

int main(void) {
	int numGroups, angleLimit;
	scanf("%d %d", &numGroups, &angleLimit);

	groupData* groupInfo = malloc((numGroups * 2) * sizeof(groupData));

	for (int i = 0; i < numGroups; i++) {
		int xCoord, yCoord, groupSize;
		scanf("%d %d %d", &xCoord, &yCoord, &groupSize);

		double calculatedAngle = atan2(yCoord, xCoord) * 180 / PI;
		if (calculatedAngle < 0) {
			calculatedAngle += 360;
		}

		groupInfo[i].members = groupSize;
		groupInfo[i].theta = calculatedAngle;
		groupInfo[i + numGroups].members = groupSize;
		groupInfo[i + numGroups].theta = calculatedAngle + 360;
	}

	angleSort(groupInfo, 0, numGroups * 2);

	int leastMembers = groupInfo[0].members, totalMembers = 0, start = 0, end = 0;
	double maxTheta = 0;

	while (end < (numGroups * 2)) {
		if (groupInfo[end].theta - groupInfo[start].theta <= angleLimit) {
			totalMembers += groupInfo[end].members;
			end++;
		} else {
			totalMembers -= groupInfo[start].members;
			start++;
		}

		if (totalMembers < leastMembers) {
			leastMembers = totalMembers;
			maxTheta = groupInfo[end].theta - groupInfo[start - 1].theta;
		}

		if (maxTheta <= 90) {
			maxTheta = 90;
		}
	}

	printf("%d\n%.4lf\n", leastMembers, maxTheta);
	free(groupInfo);

	return 0;
}

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About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}