Test results - Codility

Tasks Details

medium

1. NumberOfDiscIntersections

Compute the number of intersections in a sequence of discs.

81%

100%

62%

We draw N discs on a plane. The discs are numbered from 0 to N − 1. An array A of N non-negative integers, specifying the radiuses of the discs, is given. The J-th disc is drawn with its center at (J, 0) and radius A[J].

We say that the J-th disc and K-th disc intersect if J ≠ K and the J-th and K-th discs have at least one common point (assuming that the discs contain their borders).

The figure below shows discs drawn for N = 6 and A as follows:

A[0] = 1 A[1] = 5 A[2] = 2 A[3] = 1 A[4] = 4 A[5] = 0

There are eleven (unordered) pairs of discs that intersect, namely:

discs 1 and 4 intersect, and both intersect with all the other discs;

disc 2 also intersects with discs 0 and 3.

Write a function:

function solution(A);

that, given an array A describing N discs as explained above, returns the number of (unordered) pairs of intersecting discs. The function should return −1 if the number of intersecting pairs exceeds 10,000,000.

Given array A shown above, the function should return 11, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..100,000];

each element of array A is an integer within the range [0..2,147,483,647].

Solution

Programming language used JavaScript

Time spent on task 11 minutes

Notes

not defined yet

Task timeline

Code: 06:07:42 UTC, js, verify, result: Failed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 6.4.0)
    var array = new Array();
			for(var i = 0 ; i < A.length; i++){
			    var pos = {
			        start : i - A[i],
					end   : i + A[i]
				};

			    array.push(pos);
			};

			var crossCnt = 0;
			for(var i = 0 ; i < array.length -1 ; i++){
				for(var j = 1; j < array.length ; j++){
				    //기준 시작점이 비교대상 시작점보다 작거가 같고 비교대상 끝점보다 크거나 같을때
					if( i != j && i < j){
                        if((array[i].start < array[j].start && array[i].end >= array[j].start) || (array[i].start <= array[j].end && array[i].end > array[j].end)){
                            crossCnt++;
							// console.log("(" + i + "," + j + ")");
                        }else if(array[i].start > array[j].start && array[i].end <= array[j].end){
                            crossCnt++;
                            // console.log("!!(" + i + "," + j + ")");
						}
					}
				}
			};

			return crossCnt;
}

Analysis

▶

example1
example test

✘

WRONG ANSWER
got 10 expected 11

Code: 06:17:35 UTC, js, verify, result: Passed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 6.4.0)
     var array = new Array();
			for(var i = 0 ; i < A.length; i++){
			    var pos = {
			        start : i - A[i],
					end   : i + A[i]
				};

			    array.push(pos);
			};

			var crossCnt = 0;
			for(var i = 0 ; i < array.length -1 ; i++){
				for(var j = 1; j < array.length ; j++){
				    //기준 시작점이 비교대상 시작점보다 작거가 같고 비교대상 끝점보다 크거나 같을때
                    // if( i != j && i < j){
                     //    if((array[i].start < array[j].start && array[i].end >= array[j].start) || (array[i].start <= array[j].end && array[i].end > array[j].end)){
                     //        crossCnt++;
						// 	console.log("(" + i + "," + j + ")");
                     //    }else if(array[i].start > array[j].start && array[i].end <= array[j].end){
                     //        crossCnt++;
                     //        console.log("!(" + i + "," + j + ")");
						// }else if(array[i].start < array[j].end && array[i].end < array[j].end){
                     //        crossCnt++;
                     //        console.log("!!(" + i + "," + j + ")");
						// }
                    // }

					if(array[i].end >= array[j].start && i < j){
					// if(){
                        crossCnt++;
					}

					// }

				}
			};

			return crossCnt;
}

Analysis

▶

example1
example test

✔

Code: 06:17:39 UTC, js, verify, result: Passed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 6.4.0)
     var array = new Array();
			for(var i = 0 ; i < A.length; i++){
			    var pos = {
			        start : i - A[i],
					end   : i + A[i]
				};

			    array.push(pos);
			};

			var crossCnt = 0;
			for(var i = 0 ; i < array.length -1 ; i++){
				for(var j = 1; j < array.length ; j++){
				    //기준 시작점이 비교대상 시작점보다 작거가 같고 비교대상 끝점보다 크거나 같을때
                    // if( i != j && i < j){
                     //    if((array[i].start < array[j].start && array[i].end >= array[j].start) || (array[i].start <= array[j].end && array[i].end > array[j].end)){
                     //        crossCnt++;
						// 	console.log("(" + i + "," + j + ")");
                     //    }else if(array[i].start > array[j].start && array[i].end <= array[j].end){
                     //        crossCnt++;
                     //        console.log("!(" + i + "," + j + ")");
						// }else if(array[i].start < array[j].end && array[i].end < array[j].end){
                     //        crossCnt++;
                     //        console.log("!!(" + i + "," + j + ")");
						// }
                    // }

					if(array[i].end >= array[j].start && i < j){
					// if(){
                        crossCnt++;
					}

					// }

				}
			};

			return crossCnt;
}

Analysis

▶

example1
example test

✔

Code: 06:17:41 UTC, js, final, score: 81

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 6.4.0)
     var array = new Array();
			for(var i = 0 ; i < A.length; i++){
			    var pos = {
			        start : i - A[i],
					end   : i + A[i]
				};

			    array.push(pos);
			};

			var crossCnt = 0;
			for(var i = 0 ; i < array.length -1 ; i++){
				for(var j = 1; j < array.length ; j++){
				    //기준 시작점이 비교대상 시작점보다 작거가 같고 비교대상 끝점보다 크거나 같을때
                    // if( i != j && i < j){
                     //    if((array[i].start < array[j].start && array[i].end >= array[j].start) || (array[i].start <= array[j].end && array[i].end > array[j].end)){
                     //        crossCnt++;
						// 	console.log("(" + i + "," + j + ")");
                     //    }else if(array[i].start > array[j].start && array[i].end <= array[j].end){
                     //        crossCnt++;
                     //        console.log("!(" + i + "," + j + ")");
						// }else if(array[i].start < array[j].end && array[i].end < array[j].end){
                     //        crossCnt++;
                     //        console.log("!!(" + i + "," + j + ")");
						// }
                    // }

					if(array[i].end >= array[j].start && i < j){
					// if(){
                        crossCnt++;
					}

					// }

				}
			};

			return crossCnt;
}

Analysis summary

The following issues have been detected: timeout errors.

Analysis

Detected time complexity:

O(N**2)

▶

example1
example test

✔

▶

simple1

✔

▶

simple2

✔

▶

simple3

✔

▶

extreme_small
empty and [10]

✔

▶

small1

✔

▶

small2

✔

▶

small3

✔

▶

overflow
arithmetic overflow tests

✔

▶

medium1

✔

▶

medium2

✔

▶

medium3

✔

▶

medium4

✔

▶

10M_intersections
10.000.000 intersections

✔

▶

big1

✘

TIMEOUT ERROR
running time: 4.58 sec., time limit: 0.61 sec.

▶

big2

✘

TIMEOUT ERROR
running time: >6.00 sec., time limit: 0.66 sec.

▶

big3
[0]*50000

✘

TIMEOUT ERROR
running time: >6.00 sec., time limit: 0.70 sec.