leetcode刷题系列/1

#include <iostream>
using namespace std;
#include  <climits>//INT_MAX

int main()
{
    int x=123;
    int res=0;
    do{
        if(res>INT_MAX/10 || res<INT_MIN/10)//判断溢出
            return 0;
        res = res*10 + x%10;
    }while(x/=10);

    cout<<res<<endl;
}

#include <iostream>
using namespace std;
#include  <climits>//INT_MAX

//搞后一半就行 与前一半比较是否相等

int main()
{
    bool ress=false;
    int  input=123321;
    //当input<0,最后一位是0第一位也得是0,所以只有0
    if(input<0 || (input%10==0 && input!=0))
        return false;

     int res=0;
    do{
        if(res>INT_MAX/10 || res<INT_MIN/10)//判断溢出
            return false;
        res = res*10 + input%10;
        input/=10;
    }while(input > res);
    
    //当输入的长度为奇数 res/10去除中位的数字 最中间的数字不影响回文的判断
    ress = (input == res || input ==res/10);

    cout<<ress<<endl;
}

int main()
{
    string input="({[]})";
    unordered_map<char,char> match = {{'(',')'},{'{','}'},{'[',']'}};
    int n=0;
    while(n<input.size())
    {    
        cout<<"1"<<input[n]<<" "<<match[input[n]]<<" "<<input[n+1]<<endl;
        if(match[input[n]] == input[n+1] && input[n+1] != '\0')
        {
            input.erase(n,2);//
            n=-1;
        }
        n++;
    }
    cout<<!input.size()<<endl;
}

//辅助栈，效率高
#include <iostream>
using namespace std;
#include <unordered_map>
#include <string>
#include <stack>

int main()
{
    string input="({[]})";
    unordered_map<char,char> match = {{')','('},{'}','{'},{']','['}};
    stack<char> re;
    cout<<re.empty()<<endl;
    bool result;
    for(char in:input)
    {   
         cout<<in<<" "<<match[in]<<endl;
        if(in=='(' || in=='{' || in=='[')
            re.push(in);
        else
        {    
            if(re.empty() || re.top() != match[in])
                result=0;
            else
                re.pop();
        }
    }
    result=re.empty();
    cout<<result<<endl;
}