Java solution to Codility Triangle problem (Lesson 6 – Sorting) which scored 100%. The problem is to determine whether a triangle can be built from a given set of edges. The strategy is to sort the array of integers and then check from the end if previous 2 elements have sum > current element.
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import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Triangle {
public int solution(int[] A) {
if(A.length < 3) return 0;
List aList = new ArrayList();
for(int i=0; i<A.length; i++) { aList.add(A[i]); } Collections.sort(aList); //made long array because each int element can be as high as Integer.MAX_VALUE so when add them //can overflow int long [] aOrdered = new long[A.length]; int index = 0; for(Integer i : aList) { aOrdered[index++] = i; } //start from the end (largest) //if previous 2 elements have sum > current element, found a triangle
for(int i=aOrdered.length-1; i>=2; i--) {
if(aOrdered[i-1] + aOrdered[i-2] > aOrdered[i]) {
return 1;
}
}
return 0;
}
}
TestNG test cases for this problem which all passed:
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import org.testng.Assert;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
import com.codility.lesson06.sorting.Triangle;
public class TriangleTests {
private Triangle solution;
@BeforeTest
public void setUp() {
solution = new Triangle();
}
@DataProvider(name = "test1")
public Object [][] createData1() {
return new Object [][] {
new Object [] { new int [] { 10, 2, 5, 1, 8, 20 }, 1 },
new Object [] { new int [] { 10, 50, 5, 1 }, 0 },
new Object [] { new int [] { 1 }, 0 },
new Object [] { new int [] { 1, 1 }, 0 },
new Object [] { new int [] { 1, 1, 1, 1 }, 1 }, //1 + 1 > 1
new Object [] { new int [] { -5, -3, -1, 2, 3, 5 }, 0 },
new Object [] { new int [] { -5, -3, -1, 2, 4, 5 }, 1 },
new Object [] { new int [] { Integer.MAX_VALUE, Integer.MAX_VALUE, Integer.MAX_VALUE }, 1 },
new Object [] { new int [] { Integer.MAX_VALUE, Integer.MAX_VALUE-1, Integer.MAX_VALUE-1 }, 1 },
};
}
@Test(dataProvider = "test1")
public void verifySolution(int[] pA, int pExpected) {
Assert.assertEquals(solution.solution(pA), pExpected);
}
}