【八月】每日一题 - 640. 求解方程

输入: equation = "x+5-3+x=6+x-2"
输出: "x=2"

输入: equation = "x=x"
输出: "Infinite solutions"

输入: equation = "2x=x"
输出: "x=0"

var solveEquation = function(equation) {
    let equaIndex = equation.indexOf('=')
    let [leftNum,leftXNum] = getNum(0,equaIndex - 1,equation)
    let [rightNum,rightXNum] = getNum(equaIndex + 1,equation.length - 1,equation)
    let num = leftNum - rightNum
    let xNum = rightXNum - leftXNum
    if(xNum === 0 && num !== 0){
        return 'No solution'
    }
    return xNum === 0 ? 'Infinite solutions' : ('x=' + num / xNum)
};
function getNum(start,end,str){
    let sum = 0, xNum = 0
    let temp = ''
    for(let i = start; i <= end; i++){
        if(str[i] === 'x'){
            if(temp !=='' && temp !== '+' && temp !== '-'){
                xNum += Number(temp)
            }else{
                xNum += Number(temp + 1)
            }
            temp = ''
        }else if(str[i] === '+' || str[i] === '-'){
            sum += Number(temp)
            temp = str[i]
        }else{
            temp += str[i]
        }
    }
    sum += Number(temp) // 需要注意的是如果最后一个为数字的话，会被我们缓存，而没有进行计算
    return [sum,xNum]
}