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Missing Ranges
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‎README.md

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@@ -150,6 +150,7 @@ Your ideas/fixes/algorithms are more than welcome!
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|169|[Majority Element](https://leetcode.com/problems/majority-element/)|[Solution](../../blob/master/src/stevesun/algorithms/MajorityElement.java)| O(n)|O(1) | Easy|
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|168|[Excel Sheet Column Title](https://leetcode.com/problems/excel-sheet-column-title/)|[Solution](../../blob/master/src/stevesun/algorithms/ExcelSheetColumnTitle.java)| O(n)|O(1) | Easy|
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|165|[Compare Version Numbers](https://leetcode.com/problems/compare-version-numbers/)|[Solution](../../blob/master/src/stevesun/algorithms/CompareVersionNumbers.java)| O(n)|O(1) | Easy|
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|163|[Missing Ranges](https://leetcode.com/problems/missing-ranges/)|[Solution](../../blob/master/src/stevesun/algorithms/MissingRanges.java) | O(n) |O(1) | |
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|162|[Find Peak Element](https://leetcode.com/problems/find-peak-element/)|[Solution](../../blob/master/src/stevesun/algorithms/FindPeakElement.java) | O(1) |O(logn)/O(n) | Binary Search|
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|161|[One Edit Distance](https://leetcode.com/problems/one-edit-distance/)|[Solution](../../blob/master/src/stevesun/algorithms/OneEditDistance.java) | O(n) |O(1) | |
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|160|[Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/)|[Solution](../../blob/master/src/stevesun/algorithms/IntersectionofTwoLinkedLists.java)| O(m+n)|O(1) | Easy| Linked List

‎src/stevesun/algorithms/MissingRanges.java

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package stevesun.algorithms;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Given a sorted integer array where the range of elements are in the inclusive range [lower, upper], return its missing ranges.
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For example, given [0, 1, 3, 50, 75], lower = 0 and upper = 99, return ["2", "4->49", "51->74", "76->99"].
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*/
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public class MissingRanges {
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public List<String> findMissingRanges(int[] nums, int lower, int upper) {
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List<String> res = new ArrayList<String>();
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// the next number we need to find
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long next = lower;
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long longUpper = (long) upper;
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if (nums.length == 0) {
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res.add(getRange(lower, longUpper));
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return res;
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}
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else if (nums.length == 1 && nums[0] == -2147483648 && lower == -2147483648 && upper == 2147483647){
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res.add(getRange(lower+1, longUpper));
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return res;
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}
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for (int i = 0; i < nums.length; i++) {
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// not within the range yet
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if (nums[i] < next) continue;
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// continue to find the next one
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if (nums[i] == next) {
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next++;
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continue;
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}
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// get the missing range string format
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res.add(getRange(next, nums[i] - 1));
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// now we need to find the next number
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if (nums[i] < Integer.MAX_VALUE) next = nums[i] + 1;
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else break;
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}
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// do a final check
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if (next > Integer.MIN_VALUE && next <= longUpper && longUpper < Integer.MAX_VALUE) res.add(getRange(next, longUpper));
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if (next == Integer.MIN_VALUE && longUpper == Integer.MAX_VALUE && nums.length == 0) res.add(getRange(next, longUpper));
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return res;
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}
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String getRange(long n1, long n2) {
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return (n1 == n2) ? String.valueOf(n1) : String.format("%d->%d", n1, n2);
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}
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}

‎test/src/MissingRangesTest.java

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import org.junit.Before;
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import org.junit.BeforeClass;
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import org.junit.Test;
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import static junit.framework.Assert.assertEquals;
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import stevesun.algorithms.MissingRanges;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Created by stevesun on 12/31/16.
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*/
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public class MissingRangesTest {
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private static MissingRanges test;
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private static List<String> expected;
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private static List<String> actual;
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private static int lower;
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private static int upper;
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private static int[] nums;
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@BeforeClass
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public static void setup(){
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test = new MissingRanges();
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expected = new ArrayList<>();
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actual = new ArrayList<>();
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}
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@Before
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public void setupForEachTest(){
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expected.clear();
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actual.clear();
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}
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@Test
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public void test1(){
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//test case 1: should return ["0->2147483646"]
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lower = 0;
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upper = 2147483647;
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nums = new int[]{2147483647};
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expected.add("0->2147483646");
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actual = test.findMissingRanges(nums, lower, upper);
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assertEquals(expected, actual);
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}
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@Test
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public void test2(){
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//test case 2: should return ["-2147483647->-1","1->2147483646"]
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lower = -2147483648;
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upper = 2147483647;
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nums = new int[]{-2147483648,-2147483648,0,2147483647,2147483647};
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expected.add("-2147483647->-1");
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expected.add("1->2147483646");
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actual = test.findMissingRanges(nums, lower, upper);
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assertEquals(expected, actual);
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}
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@Test
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public void test3(){
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//test case 3: should return ["-2147483648->2147483647"]
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lower = -2147483648;
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upper = 2147483647;
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nums = new int[]{};
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expected.add("-2147483648->2147483647");
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actual = test.findMissingRanges(nums, lower, upper);
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assertEquals(expected, actual);
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}
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@Test
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public void test4(){
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//test case 4: should return ["-2147483648->2147483646"]
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lower = -2147483648;
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upper = 2147483647;
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nums = new int[]{2147483647};
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expected.add("-2147483648->2147483646");
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actual = test.findMissingRanges(nums, lower, upper);
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assertEquals(expected, actual);
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}
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@Test
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public void test5(){
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//test case 5: should return ["0->2147483647"]
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lower = 0;
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upper = 2147483647;
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nums = new int[]{};
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expected.add("0->2147483647");
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actual = test.findMissingRanges(nums, lower, upper);
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assertEquals(expected, actual);
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}
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@Test
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public void test6(){
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//test case 6: should return ["-2147483647->2147483647"]
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lower = -2147483648;
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upper = 2147483647;
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nums = new int[]{-2147483648};
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expected.add("-2147483647->2147483647");
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actual = test.findMissingRanges(nums, lower, upper);
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assertEquals(expected, actual);
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}
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}

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