LintCode 1315: Summary Ranges

原创于 2020-03-20 14:58:17 发布 · 86 阅读

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本文介绍了一种用于处理已排序无重复整数数组的算法，该算法能高效地将连续的整数序列汇总为区间字符串。例如，对于输入[0,1,2,4,5,7]，输出为[“0->2”, “4->5”, “7”]。通过一次遍历，算法判断相邻元素是否连续，从而实现区间合并。

Summary Ranges

Given a sorted integer array without duplicates, return the summary of its ranges.

Example
Example1

Input: [0,1,2,4,5,7]
Output: [“0->2”,“4->5”,“7”]
Example2

Input: [0,2,3,4,6,8,9]
Output: [“0”,“2->4”,“6”,“8->9”]
Notice
The result is in ascending order

解法1：

class Solution {
public:
    /**
     * @param nums:  a sorted integer array without duplicates
     * @return: the summary of its ranges
     */
    vector<string> summaryRanges(vector<int> &nums) {
        int n = nums.size();
        if (n == 0) return {};
        vector<string> result;
        int pos = 0;
        for (int i = 0; i < n; ++i) {
            if (i + 1 < n && nums[i + 1] > nums[i] + 1) {
                if (i == pos) 
                    result.push_back(to_string(nums[i]));
                else
                    result.push_back(to_string(nums[pos]) + "->" + to_string(nums[i]));
                pos = i + 1;    
            }
        }
        if (pos == n - 1)
            result.push_back(to_string(nums[pos]));
        else
            result.push_back(to_string(nums[pos]) + "->" + to_string(nums[n - 1]));
        
        return result;
    }
};