Algorithm
Problem Name: 228. Summary Ranges
You are given a sorted unique integer array nums.
A range [a,b] is the set of all integers from a to b (inclusive).
Return the smallest sorted list of ranges that cover all the numbers in the array exactly. That is, each element of nums is covered by exactly one of the ranges, and there is no integer x such that x is in one of the ranges but not in nums.
Each range [a,b] in the list should be output as:
"a->b"ifa != b"a"ifa == b
Example 1:
Input: nums = [0,1,2,4,5,7] Output: ["0->2","4->5","7"] Explanation: The ranges are: [0,2] --> "0->2" [4,5] --> "4->5" [7,7] --> "7"
Example 2:
Input: nums = [0,2,3,4,6,8,9] Output: ["0","2->4","6","8->9"] Explanation: The ranges are: [0,0] --> "0" [2,4] --> "2->4" [6,6] --> "6" [8,9] --> "8->9"
Constraints:
0 <= nums.length <= 20-231 <= nums[i] <= 231 - 1- All the values of
numsare unique. numsis sorted in ascending order.
Code Examples
#1 Code Example with C Programming
Code -
C Programming
void ranges(int *nums, int numsz, int ***pp, int *sz, int *n) {
int a, b;
int i, l;
char buff[64];
if (numsz == 0) return;
if (*n == *sz) {
(*sz) *= 2;
(*pp) = realloc(*pp, (*sz) * sizeof(char *));
//assert(*pp);
}
b = a = nums[0];
i = 1;
while (i < numsz && (b + 1) == nums[i]) {
i ++; b ++;
}
l = sprintf(buff, "%d", a);
if (i > 1) {
l += sprintf(&buff[l], "->%d", b);
}
(*pp)[*n] = malloc((l + 1) * sizeof(char));
strcpy((*pp)[*n], buff);
(*n) ++;
ranges(&nums[i], numsz - i, pp, sz, n);
}
char** summaryRanges(int* nums, int numsSize, int* returnSize) {
int sz, n;
char **p;
*returnSize = 0;
if (numsSize == 0) return NULL;
sz = 100;
p = malloc(sz * sizeof(char *));
n = 0;
ranges(nums, numsSize, &p, &sz, &n);
*returnSize = n;
return p;
}
Input
Output
#2 Code Example with C++ Programming
Code -
C++ Programming
class Solution {
public:
vector<string> summaryRanges(vector<int>& nums) {
vector < string>res;
for(int i = 0, j = 1; i < nums.size(); i = j, j = i + 1){
while(j < nums.size() && nums[j] == nums[j - 1] + 1) j++;
res.push_back((j == i + 1) ? to_string(nums[i]) : to_string(nums[i]) + "->" + to_string(nums[j - 1]));
}
return res;
}
};
Input
Output
#3 Code Example with Java Programming
Code -
Java Programming
class Solution {
public List summaryRanges(int[] nums) {
List result = new ArrayList<>();
int idx = 0;
int n = nums.length;
while (idx < n) {
int start = nums[idx];
int end = start;
idx++;
while (idx < n && nums[idx] == end + 1) {
end = nums[idx];
idx++;
}
result.add(start == end ? String.valueOf(start) : (start + "->" + end));
}
return result;
}
}
Input
Output
#4 Code Example with Javascript Programming
Code -
Javascript Programming
const summaryRanges = function(nums) {
if (nums == null || nums.length === 0) return []
const res = []
if (nums.length === 1) return [`${nums[0]}`]
let start = nums[0]
let end = nums[0]
let endVal = end
for (let i = 1, len = nums.length; i < len; i++) {
let cur = nums[i]
if (cur - end > 1) {
endVal = end
insert(res, start, end)
start = cur
end = cur
} else {
end = cur
}
}
if (endVal !== end) {
insert(res, start, end)
}
return res
}
function insert(arr, start, end) {
if (start === end) {
arr.push(`${start}`)
} else {
arr.push(`${start}->${end}`)
}
}
Input
Output
#5 Code Example with Python Programming
Code -
Python Programming
class Solution:
def summaryRanges(self, nums):
"""
:type nums: List[int]
:rtype: List[str]
"""
res, stack = [], [nums[0] if nums else None, None]
for i, num in enumerate(nums):
if i > 0 and nums[i - 1] == num - 1: stack[1] = num
if i > 0 and nums[i-1] != num - 1: res, stack[0], stack[1] = res + ["->".join(str(q) for q in stack if q != None)], num, None
if i == len(nums) - 1: res.append("->".join(str(q) for q in stack if q != None))
return res
Input
Output