代码随想录算法训练营第十一天 | ● 20. 有效的括号 ● 1047. 删除字符串中的所有相邻重复项 ● 150. 逆波兰表达式求值

今日学习的内容

● 20. 有效的括号

var isValid = function(s) {
    let stack = [] ;
    for(let i = 0 ;i < s.length ; i++){
        let temp = s[i];
        if(temp == '('){
            stack.push(')')
            continue;
        }
        if(temp == '['){
            stack.push(']');
              continue;
        }
        if(temp == '{'){
            stack.push('}')
        }else{
            if(temp != stack.pop()){
                return false
            }
        }
    }
    console.log(stack,90)
    return stack.length ==0 

};

● 1047. 删除字符串中的所有相邻重复项

var removeDuplicates = function(s) {
    let stack = [] ;
    s = Array.from(s);
    for(let i = 0 ;i < s.length ;i++){
        if(stack[stack.length-1] == s[i]){
            stack.pop()
        }else{
            stack.push(s[i])
        }
        
    }
    return stack.join('')

};

● 150. 逆波兰表达式求值

var evalRPN = function(tokens) {
    let stack = [] ;
    let obj = {
        '+':1,
        '-':1,
        '*':1,
        '/':1
    }
    let res =0
    for(let i = 0 ; i < tokens.length ; i++){
        if(obj[tokens[i]]){
            let a = stack.pop();
            let b = stack.pop();
            if(tokens[i] == '+'){
                res = a/1+b/1
            }
            if(tokens[i] == '-'){
                res = b/1-a/1
            }
            if(tokens[i] == '*'){
                res = a*b
            }
            if(tokens[i] == '/'){
                console.log(a,b)
                res = b/a|0
                // res = Math.floor(b*1/a) ||0
            }
            stack.push(res)
        }else{
            stack.push(tokens[i])
        }
        console.log(stack)
    }
    // console.log(stack)
    return stack.pop()
};