[LeetCode 228] Summary Ranges

Mavs

于 2015-09-24 04:07:18 发布

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分类专栏： Leetcode Java 文章标签： leetcode array

本文链接：https://blog.youkuaiyun.com/sbitswc/article/details/48704025

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本文介绍了一种针对已排序且不含重复元素的整数数组，实现区间汇总的有效算法。该算法采用双指针技术扫描数组，当遇到不连续的数字时记录区间，并重置指针继续扫描。通过具体实例演示了如何将输入数组转换为简洁的区间表达形式。

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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:

use two pointer, scan from begin, if jumped then store result and reset two pointer.

public class Solution {
    public List<String> summaryRanges(int[] nums) {
        List<String> res = new ArrayList<String>();
        if(nums.length<=0) return res;
        int start = 0;
        int end = 1;
        while(end<nums.length) {
            if(nums[end] - nums[end-1] == 1) {
                end++;
                continue;
            }else {
                String s1 = String.valueOf(nums[start]);
                if(start+1 != end) s1 = s1+"->" + String.valueOf(nums[end-1]);
                res.add(s1);
                start = end;
                end++;
            }
        }
        if(start+1 == end) res.add(String.valueOf(nums[start]));
        else {
            String s1 = String.valueOf(nums[start]) + "->" + String.valueOf(nums[end-1]);
            res.add(s1);
        }
        return res;
    }
}