Reverse Integer

最新推荐文章于 2022-09-18 19:57:18 发布

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最新推荐文章于 2022-09-18 19:57:18 发布

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原文链接：http://www.cnblogs.com/SpeakSoftlyLove/p/5097307.html

本文介绍了两种反转整数的方法，旨在减少字符串转换带来的性能损耗。通过直接操作整数数组来实现快速反转，同时考虑了正负号的处理及整数溢出问题。

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Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

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两种方法，第一种比较耗时间，应该是在转换为字符串的时候浪费了时间

class Solution {
public:
    
    void reverse_str(string &s, int begin, int end)
    {
        int i ,j;
        char c;
        for (i=begin,j=end;i<j;i++,j--)
        {
            c = s[i];
            s[i] = s[j];
            s[j] = c;
            
        }
    }
    int reverse(int x) {
        if (x>=0 && x<=9)
            return x;
        stringstream ss;
        ss << x;
        string str = ss.str();
        int len = str.size();
        if (x > 0)
        {
            reverse_str(str,0,len-1);
        }
        else
        {
            reverse_str(str,1,len-1);
        }
        stringstream sss(str);
        double r =0;
        sss >> r;
        if (r>INT_MAX || r<INT_MIN) {
            r = 0;
        }
        return (int)r;
    }
};

class Solution {
public:
    
    void reverse_str(string &s, int begin, int end)
    {
        int i ,j;
        char c;
        for (i=begin,j=end;i<j;i++,j--)
        {
            c = s[i];
            s[i] = s[j];
            s[j] = c;
            
        }
    }
    int reverse(int x) {
        if (x>=0 && x<=9)
            return x;
        stringstream ss;
        ss << x;
        string str = ss.str();
        int len = str.size();
        if (x > 0)
        {
            reverse_str(str,0,len-1);
        }
        else
        {
            reverse_str(str,1,len-1);
        }
        stringstream sss(str);
        double r =0;
        sss >> r;
        if (r>INT_MAX || r<INT_MIN) {
            r = 0;
        }
        return (int)r;
    }
};