2021-08-17

Posted 2022-12-09 李憨憨_

练习一

JZ49把字符串转换成整数
题目描述：

class Solution 
public:
    int StrToInt(string str) 
        if(str.empty())
            return 0;
        int flag = 1;
        int sum = 0;
        if(str[0] == '-')
        
            flag = -1;
            str[0] = '0';
        
        else if(str[0] == '+')
        
            flag = 1;
            str[0] = '0';
        
        for(int i = 0; i < str.size(); ++i)
        
            if(str[i] < '0' || str[i] > '9')
                return 0;
            sum = sum * 10 + str[i] - '0';
        
        return sum * flag;
    
;

练习二

WY22 Fibonacci数列
题目描述：

#include <iostream>
using namespace std;

int main()

    int f, f1 = 0, f2 = 1;
    int N, left = 0, right = 0;
    cin >> N;
    while(1)
    
        f = f1 + f2;
        f1 = f2;
        f2 = f;
        if(f < N)
        
            left = f;
        
        else
        
            right = f;
            break;
        
    
    cout << min(N - left, right - N) << endl;
    return 0;

练习三

CM46 合法括号序列判断
题目描述：

class Parenthesis 
public:
    bool chkParenthesis(string A, int n) 
        // write code here
        stack<char> sc;
        for(auto& ch : A)
        
            switch(ch)
            
                case '(':
                    sc.push(ch);
                    break;
                case ')':
                    if(sc.empty())
                        return false;
                    sc.pop();
                    break;
                default:
                    return false;
            
        
        return sc.empty();
    
;