Summary Ranges

Author: int32bit

README.md

@@ -125,6 +125,7 @@
 + [217 Contains Duplicate(hashset)](algorithms/ContainsDuplicate)
 + [219 Contains Duplicate II(hashmap)](algorithms/ContainsDuplicateII)
 + [226 Invert Binary Tree(递归，树)](algorithms/InvertBinaryTree)
++ [228 Summary Ranges](algorithms/SummaryRanges)
 + [231 Power of Two(位运算，二进制1的个数)](algorithms/PowerofTwo)
 
 ## Database

algorithms/SummaryRanges/README.md

@@ -0,0 +1,47 @@
+## Summary Ranges
+
+Given a sorted integer array without duplicates, return the summary of its ranges.
+
+For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].
+
+Credits:
+Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.
+
+## Solution
+
+直接遍历数组即可
+
+```cpp
+vector<string> summaryRanges(vector<int> &nums) {
+	vector<string> result;
+	int n = nums.size();
+	if (n == 0) {
+		return result;
+	}
+	int s = nums[0], t;
+	bool update = false;
+	int i;
+	for (i = 1; i < n; ++i) {
+		if (nums[i] == nums[i - 1] + 1) {
+			update = true;
+			t = nums[i];
+		} else {
+			if (update) {
+				result.push_back(to_string(s) + "->" + to_string(t));
+				s = nums[i];
+				update = false;
+			} else {
+				result.push_back(to_string(s));
+				s = nums[i];
+			}
+		}
+	}
+	// last update
+	if (update) {
+		result.push_back(to_string(s) + "->" + to_string(nums[n - 1]));
+	} else {
+		result.push_back(to_string(nums[n - 1]));
+	}
+	return result;
+}
+```

algorithms/SummaryRanges/solve.cpp

@@ -0,0 +1,48 @@
+#include <string>
+#include <vector>
+#include <iostream>
+#include <algorithm>
+#include <cstdio>
+using namespace std;
+class Solution {
+	public:
+		vector<string> summaryRanges(vector<int> &nums) {
+			vector<string> result;
+			int n = nums.size();
+			if (n == 0) {
+				return result;
+			}
+			int s = nums[0], t;
+			bool update = false;
+			int i;
+			for (i = 1; i < n; ++i) {
+				if (nums[i] == nums[i - 1] + 1) {
+					update = true;
+					t = nums[i];
+				} else {
+					if (update) {
+						result.push_back(to_string(s) + "->" + to_string(t));
+						s = nums[i];
+						update = false;
+					} else {
+						result.push_back(to_string(s));
+						s = nums[i];
+					}
+				}
+			}
+			if (update) {
+				result.push_back(to_string(s) + "->" + to_string(nums[n - 1]));
+			} else {
+				result.push_back(to_string(nums[n - 1]));
+			}
+			return result;
+		}
+};
+int main(int argc, char **argv)
+{
+	Solution solution;
+	vector<int> nums = {0,5,9};
+	auto result = solution.summaryRanges(nums);
+	for_each(begin(result), end(result), [](string s) {cout << s << endl;});
+	return 0;
+}