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Java Solution for LeetCode algorithm problems, continually updating
package g0201_0300.s0228_summary_ranges;
// #Easy #Array #2022_07_04_Time_0_ms_(100.00%)_Space_42.7_MB_(15.43%)
import java.util.ArrayList;
import java.util.List;
public class Solution {
public List summaryRanges(int[] nums) {
List ranges = new ArrayList<>();
if (nums.length == 0) {
return ranges;
}
// size of array
int n = nums.length;
// start of range
int a = nums[0];
// end of range
int b = a;
StringBuilder strB = new StringBuilder();
for (int i = 1; i < n; i++) {
// we need to make a decision if the next element
// will expand the range
// i starts at 1, not 0, because 1 is the next
// candidate for expanding the range
if (nums[i] != b + 1) {
// only when our next element does not expand the range
// do we add the range a->b to our list of ranges
strB.append(a);
if (a != b) {
strB.append("->").append(b);
}
ranges.add(strB.toString());
// since nums[i] is not accounted for by our range a->b
// because nums[i] is not b+1, we need to set a and b
// to this new range start point of bigger than b+1
// maybe it is b+2? b+3? b+4? all we know is it is not b+1
a = nums[i];
b = a;
// Reset string builder
strB.setLength(0);
} else {
// if the next element expands our range we do so
b++;
}
}
// the only range that is not accounted for at this point is the last range
// if our a and b are not equal then we add the range accordingly
strB.append(a);
if (a != b) {
strB.append("->").append(b);
}
ranges.add(strB.toString());
return ranges;
}
}