228. 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"].

这个题目不难，首先对原序列进行排序，然后要注意对特殊情况的处理。同时，要掌握string类的几个重要成员函数：

• to_string()：将数字转换为string对象
• append()：向string对象追加字符串

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        int n = nums.size();
        if (n == 0)
            return vector<string>();
        
        vector<string> res; 
        sort(nums.begin(), nums.end());
        for (int i = 0, j = 0; i <= j && j <= n-1; ) {
            while (j <= n-2 && nums[j+1] == nums[j] + 1) {
                ++j;
            }
            string tmp;
            if (j > i) {
                tmp.append(to_string(nums[i]));
                tmp.append("->");
                tmp.append(to_string(nums[j]));
                ++j;
                i = j;
            } else {
                tmp.append(to_string(nums[i]));
                ++i;
                ++j;
            }
            res.push_back(tmp);
        }
        return res;
    }
};