LeetCode（228） Summary Ranges

题目

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”].

分析

题目要求很明显，要求对给定的一组有序整数序列按照连续性分组显示；

一次遍历记录连续子序列的首尾元素，然后转换为string格式，整数和字符串格式类型转换需要特别注意INT_MIN时特殊处理；

AC代码

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        if (nums.empty())
            return vector<string>();

        int sz = nums.size();

        vector<string> ret;
        int start = nums[0], end = nums[0];
        for (int i = 1; i < sz; ++i)
        {
            if (nums[i] == end + 1)
                end = nums[i];
            else{
                string tmp;
                if (end == start)
                    tmp = IntToString(start);
                else
                    tmp = IntToString(start) + "->" + IntToString(end);

                ret.push_back(tmp);

                start = nums[i];
                end = nums[i];
            }
        }//for

        //加上最后一组
        string tmp;
        if (end == start)
            tmp = IntToString(start);
        else
            tmp = IntToString(start) + "->" + IntToString(end);
        ret.push_back(tmp);

        return ret;
    }

    string IntToString(long num)
    {
        if (num == 0)
            return "0";
        else if (num == INT_MIN)
            return "-2147483648";
        string str;
        bool flag = num < 0 ? false : true;

        num = abs(num);
        while (num)
        {
            char c = num % 10 + '0';
            num /= 10;
            str += c;
        }//while
        reverse(str.begin(), str.end());

        if (flag)
            return str;
        else
            return "-" + str;
    }
};

GitHub测试程序源码