js 栈实现四则运算 wip
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class Stack {
constructor() {
this.items = [];
}
pop() {
return this.items.pop();
}
push(data) {
this.items.push(data);
}
getTop() {
return this.items.length > 0 ? this.items[this.items.length - 1] : '';
}
isEmpty() {
return this.items.length == 0;
}
}
let operatorStack = new Stack(); // 符号栈
let numStack = new Stack(); // 数字栈
function isNum(str) {
return !['+', '-', '*', '/'].includes(str);
}
function isOperater(str) {
return ['+', '-', '*', '/'].includes(str);
}
function isNewHeight(oldValue, newValue) {
if (['*', '/'].includes(oldValue)) {
return true;
} else if (['*', '/'].includes(oldValue)) {
return false;
}
}
function calc(a, op, b) {
switch (op) {
case '+':
return a + b;
case '-':
return a - b;
case '*':
return a * b;
case '/':
return a / b;
default:
return 0;
}
}
// 计算 1+2*3+4-5
let arr = [1, '+', 2, '*', 3, '+', 4, '-', 5];
let i = 0;
while (arr[i]) {
if (isNum(arr[i])) {
numStack.push(arr[i]);
i++;
}
if (isOperater(arr[i])) {
if (!operatorStack.isEmpty()) {
if (isNewHeight(operatorStack.getTop(), arr[i])) {
operatorStack.push(arr[i]);
i++;
} else {
let op = operatorStack.pop();
let num2 = numStack.pop();
let num1 = numStack.pop();
let result = calc(num1, op, num2);
console.log('calc1', num1, op, num2);
numStack.push(result);
}
} else {
operatorStack.push(arr[i]);
i++;
}
}
}
while (operatorStack.items.length > 0) {
let op = operatorStack.pop();
let num2 = numStack.pop();
let num1 = numStack.pop();
let result = calc(num1, op, num2);
console.log('calc2', num1, op, num2);
numStack.push(result);
}
console.log('numStack', numStack.items);
console.log('operatorStack', operatorStack.items);
JavaScript
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