leetcode 682. Baseball Game

思路就是用一个栈来存储分数，剩下的就是对栈的操作了。

class Solution {
    public int calPoints(String[] ops) {
        Stack<Integer> stack = new Stack<>();
        int sum = 0;
        for(int i = 0;i<ops.length;i++){
            String tmp = ops[i];
            if(tmp=="C"){
                int a = stack.pop();
                sum -= a;
            }else if(tmp=="D"){
                int b = stack.peek()*2;
                stack.push(b);
                sum += b;
            }else if(tmp=="+"){
                int c = stack.pop();
                int d = stack.pop();
                int e = c+d;
                sum += e;
                stack.push(d);
                stack.push(c);
                stack.push(e);
            }else{
                int res = myInt(tmp);
                stack.push(res);
                sum += res;
            }
        }
        return sum;
    }
    public static int myInt(String s){
        int result = 0;
        if(s.charAt(0)=='-'){
            for(int i=1;i<s.length();i++){
                result = result*10 + (int)(s.charAt(i)-'0');
            }
            result = result*(-1);
        }else{
            for(int i =0;i<s.length();i++){
                result = result*10 + (int)(s.charAt(i)-'0');
            }
        }
        return result;
    }
}

当OJ说结果错误时，我的世界是崩塌的，明明IDE没问题的呀。原来是对于字符串的比较要用equals，IDE应该是重载了==。还是po个正确的吧。

class Solution {
    public int calPoints(String[] ops) {
        Stack<Integer> stack = new Stack<>();
        int sum = 0;
        for(int i = 0;i<ops.length;i++){
            String tmp = ops[i];
            if(tmp.equals("C")){
                int a = stack.pop();
                sum -= a;
            }else if(tmp.equals("D")){
                int b = stack.peek()*2;
                stack.push(b);
                sum += b;
            }else if(tmp.equals("+")){
                int c = stack.pop();
                int d = stack.pop();
                int e = c+d;
                sum += e;
                stack.push(d);
                stack.push(c);
                stack.push(e);
            }else{
                int res = myInt(tmp);
                stack.push(res);
                sum += res;
            }
        }
        return sum;
    }
    public static int myInt(String s){
        int result = 0;
        if(s.charAt(0)=='-'){
            for(int i=1;i<s.length();i++){
                result = result*10 + (int)(s.charAt(i)-'0');
            }
            result = result*(-1);
        }else{
            for(int i =0;i<s.length();i++){
                result = result*10 + (int)(s.charAt(i)-'0');
            }
        }
        return result;
    }
}

其实也不用自己写个myInt。可以用Integer.valueOf(str)或者是Integer.valueOf(str).intValue()
用自己写的呢，速度快击败100%，用现成的也可以，慢一点，击败91%。

来源：CSDN

作者：爱打篮球的憨憨

链接：https://blog.csdn.net/xiaobailaji/article/details/104754866