[leetcode]227. Basic Calculator II -- JavaScript 代码

来源：互联网发布：营销数据分析书籍编辑：程序博客网时间：2024/06/03 12:45

/** * @param {string} s * @return {number} */var calculate = function(s) {    s = s.replace(new RegExp(" ","g"),"");    var len = s.length;    if(len===0){        return 0;    }    var stack = [];    var ret = 0;    var sign = 1;    var isMul = 0;    for(var i=0;i<len;i++){        var n = s.charAt(i);        if (!isNaN(parseInt(n))){            var cur = parseInt(n);            while(i+1<len && (!isNaN(parseInt(s.charAt(i+1))))){                cur = 10*cur + parseInt(s.charAt(++i));              }            if(s.charAt(i+1)=="+"||s.charAt(i+1)=="-"||s.charAt(i+1)===""){                if(stack.length===0){                    ret += sign*cur;                }else{                    if(isMul==1){                        cur = cur*stack.pop();                    }else if(isMul==-1){                        cur = Math.floor(stack.pop()/cur);                    }                    s_sign = stack.pop();                    s_ret = stack.pop();                    ret = s_ret+s_sign*cur;                    isMul = 0;                }            }else if(s.charAt(i+1)=="*"||s.charAt(i+1)=="/"){                if(isMul===0){                    stack.push(ret);                    stack.push(sign);                    stack.push(cur);                    ret = 0;                    sigh = 1;                }else{  // 3+8*9/3                    if(isMul==1){                        cur = cur*stack.pop();                        stack.push(cur);                    }else if(isMul==-1){                        cur = Math.floor(stack.pop()/cur);                        stack.push(cur);                    }                }            }        }else if(n=="+"){            sign = 1;            isMul = 0;        }else if(n=="-"){            sign = -1;            isMul = 0;        }else if(n=="*"){            isMul = 1;        }else if(n=="/"){            isMul = -1;        }    }    return ret;};

同题目Basic Calculator一样，这道题也是应用了栈来做的。
难点在于需要考虑的很周全。

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