[LeetCode] Summary Ranges

标签：c++   leetcode   

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.

解题思路：

这道题题意是，将相邻的一组数据用区间表示。虽然mark为easy，但是麻雀虽小，却五脏俱全，有很多陷阱的问题。

1、最开始想的是如下代码。但有几个问题需要注意一下。一个就是可能溢出问题，这体现在两个方面，一个是自行编写的数字转字符串的代码中，另一个是在判断两个数是否相邻。因为对c++不够了解，因此竟然不知道如何将数字转化成字符串，于是动手写了一个。囧。这个版本的代码就像懒婆娘的裹脚布一样。

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        int len = nums.size();
        vector<string> result;
        if(len == 0){
            return result;
        }
        int left = nums[0];
        nums.push_back(nums[len-1]);
        len++;
        for(int i=1; i<len; i++){
            if(nums[i] == nums[i-1] || ((long long)nums[i] - (long long)nums[i-1] > 1)){
                if(left == nums[i-1]){
                    result.push_back(intToString(left));
                }else{
                    result.push_back(intToString(left) + "->" + intToString(nums[i-1]));
                }
                left = nums[i];
            }
        }
        return result;
    }
    
    string intToString(int n){
        if(n==0){
            return "0";
        }
        long long lN = n;
        string s = "";
        if(lN<0){
            s = "-";
            lN = -lN;
        }
        stack<char> stacks;
        while(lN!=0){
            stacks.push(lN%10 + '0');
            lN = lN/10;
        }
        while(!stacks.empty()){
            s += stacks.top();
            stacks.pop();
        }
        return s;
    }
};

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        int len = nums.size();
        vector<string> result;
        if(len == 0){
            return result;
        }
        int left = nums[0];
        nums.push_back(nums[len-1]);
        len++;
        for(int i=1; i<len; i++){
            if(nums[i] == nums[i-1] || nums[i] - nums[i-1] != 1){
                if(left == nums[i-1]){
                    result.push_back(to_string(left));
                }else{
                    result.push_back(to_string(left) + "->" + to_string(nums[i-1]));
                }
                left = nums[i];
            }
        }
        return result;
    }
};

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        int len = nums.size();
        int i=0;
        vector<string> result;
        while(i<len){
            int j=1;
            while(i+j<len && nums[i+j] - nums[i] == j) j++;
            result.push_back(j==1 ? to_string(nums[i]) : to_string(nums[i]) + "->" + to_string(nums[i + j - 1]));
            i += j;
        }
        return result;
    }
};

[LeetCode] Summary Ranges

标签：c++   leetcode   

原文地址：http://blog.csdn.net/kangrydotnet/article/details/46777739