题解 | java#矩阵乘法计算量估算#

import java.util.*;
import java.util.concurrent.LinkedBlockingDeque;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int  num = in.nextInt();
        Queue<Matri> matris = new LinkedBlockingDeque<>();
        for (int i = 0; i < num; i++) {
            Matri matri = new Matri(in.nextInt(), in.nextInt());
            matris.add(matri);
        }
        Stack<Matri> stack = new Stack<>();
        String chengfa = in.next();
        int count = 0;
        for (int i = 0; i < chengfa.length() ; i++) {
            if (chengfa.charAt(i) == '(') {
                continue;
            } else if (chengfa.charAt(i) == ')') {
                if (stack.size() <=1) {
                    break;
                }
                Matri a = stack.pop();
                Matri b = stack.pop();
                count = count + b.x * b.y * a.y;
                Matri c = new Matri(b.x, a.y);
                stack.push(c);
            } else {
                stack.push(matris.poll());
            }

        }
        System.out.println(count);
    }

    public static class Matri {
        private int x;
        private int y;

        public Matri(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }

}