leetcode 640. Solve the Equation 等式计算 + C++stringstream的一个很好地示范

ゝ一世哀愁。 2022-06-03 06:42 128阅读 0赞

Solve a given equation and return the value of x in the form of string “x=\#value”. The equation contains only ‘+’, ‘-’ operation, the variable x and its coefficient.

If there is no solution for the equation, return “No solution”.

If there are infinite solutions for the equation, return “Infinite solutions”.

If there is exactly one solution for the equation, we ensure that the value of x is an integer.

Example 1:  
Input: “x+5-3+x=6+x-2”  
Output: “x=2”  
Example 2:  
Input: “x=x”  
Output: “Infinite solutions”  
Example 3:  
Input: “2x=x”  
Output: “x=0”  
Example 4:  
Input: “2x+3x-6x=x+2”  
Output: “x=-1”  
Example 5:  
Input: “x=x+2”  
Output: “No solution”

本题题意很简单，就是直接分析即可，注意使用C++的stringstream来处理，就是有点烦，别的都很简单

建议和[leetcode 609. Find Duplicate File in System C++stringstream的一个很好地示范][leetcode 609. Find Duplicate File in System C_stringstream] 一起学习

代码如下：

#include <iostream>
    #include <vector>
    #include <map>
    #include <unordered_map>
    #include <set>
    #include <unordered_set>
    #include <queue>
    #include <stack>
    #include <string>
    #include <climits>
    #include <algorithm>
    #include <sstream>
    #include <functional>
    #include <bitset>
    #include <numeric>
    #include <cmath>
    #include <regex>
    #include <iomanip>
    
    using namespace std;
    
    
    class Solution
    {
    public:
        string solveEquation(string equation)
        {
            int index = equation.find('=');
            vector<int> left = getRes(equation.substr(0, index));
            vector<int> right = getRes(equation.substr(index + 1));
    
            int x = left[0] - right[0];
            int num = right[1] - left[1];
    
            string res = "";
            if (x == 0 && num == 0)
                res = "Infinite solutions";
            else if (x == 0 && num != 0)
                res = "No solution";
            else
                res = "x=" + to_string(num / x);
    
            return res;
        }
    
        vector<int> getRes(string eq)
        {
            vector<int> res;
            stringstream ss(eq);
            char c;
            int num = 0, x = 0, tmp;
            string a = "";
    
            for (int i = 0; i <= eq.length(); i++)
            {
                if (i<eq.length())
                    ss >> c;
                if (c == '+' || c == '-' || i == eq.length())
                {
                    if (a.size() >= 1)
                    {
                        if (a.back() == 'x')
                        {
                            if (a == "x" || a == "+x")
                                tmp = 1;
                            else if (a == "-x")
                                tmp = -1;
                            else
                                tmp = stoi(a.substr(0, a.length() - 1));
                            x += tmp;
                        }
                        else
                        {
                            tmp = stoi(a);
                            num += tmp;
                        }
                    }
                    if (c == '-')
                        a = "-";
                    else
                        a = "";
                }
                else
                    a += c;
            }
            res = { x,num };
            return res;
        }
    };

[leetcode 609. Find Duplicate File in System C_stringstream]: http://blog.csdn.net/jackzhang_123/article/details/78842741