This challenge from LeetCode may be found at the following URL: https://leetcode.com/problems/summary-ranges/?tab=Description
If interested, following is a screen capture from my Eclipse IDE:
>>> N: 6 <== number of numbers that follows
0 1 2 4 5 7 <== sorted numbers
summary: [0->2, 4->5, 7]
In addition I tried the following custom test cases:
3
0 2 3
4
0 1 2 9
4
0 2 3 9
8
0 1 2 4 6 7 8 9
0
1
3
9
-12 -9 -8 -3 0 5 6 7 9
My test code in Java follows:
/**
* Test code
*/
public static void main(String[] args) {
// **** ****
Scanner sc = new Scanner(System.in);
// **** get number of entries for the array ****
System.out.print(“>>> N: “);
int N = sc.nextInt();
int[] nums = new int[N];
// **** populate array of numbers ****
for (int n = 0; n < N; n++) {
nums[n] = sc.nextInt();
}
// **** close scanner ****
sc.close();
// **** build list of numbers ****
List<String> summary = summaryRanges(nums);
System.out.print(“summary: ” + summary.toString());
}
The code for the solution follows:
/**
* Build list of ranges.
*/
static List<String> summaryRanges(int[] nums) {
List<String> summary = new ArrayList<String>();
// **** special case(s) ****
if (nums.length == 0) {
return summary;
}
if (nums.length == 1) {
summary.add(Integer.toString(nums[0]));
return summary;
}
// **** traverse list of integers ****
int startRange = 0;
for (int i = 1; i < nums.length; i++) {
// **** close current range (if needed) ****
if (nums[i – 1] + 1 != nums[i]) {
// **** range of numbers ****
if (startRange + 1 != i) {
String str = Integer.toString(nums[startRange]);
str += “->”;
str += Integer.toString(nums[i – 1]);
summary.add(str);
}
// **** single number ****
else {
summary.add(Integer.toString(nums[startRange]));
}
// **** ****
startRange = i;
}
}
// **** complete range (if needed) ****
if (startRange != -1) {
// **** single number ****
if (startRange == (nums.length – 1)) {
summary.add(Integer.toString(nums[startRange]));
}
// **** range of numbers ****
else {
String str = Integer.toString(nums[startRange]);
str += “->”;
str += Integer.toString(nums[nums.length – 1]);
summary.add(str);
}
}
// **** ****
return summary;
}
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John
john.canessa@gmail
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