题解 | #矩阵乘法计算量估算#

栈中保存字母

import java.util.Scanner;
import java.util.Stack;

// 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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int[][] nums = new int[n][2];
            for (int i = 0; i < n; i++) {
                nums[i][0] = in.nextInt();
                nums[i][1] = in.nextInt();
            }
            String str = in.next();
            Stack<Character> stack = new Stack<>();
            int ans = 0;
            for (int i = 0; i < str.length(); i++) {
                char c = str.charAt(i);
                if (c == ')') {
                    char left = '\0';
                    while (stack.peek() != '(') {
                        char right = stack.pop();
                        left = stack.pop();
                        ans += nums[left - 'A'][0] * nums[right - 'A'][0] * nums[right - 'A'][1];
                        nums[left - 'A'][1] = nums[right - 'A'][1];
                    }
                    stack.pop();
                    stack.push(left);
                } else {
                    stack.push(c);
                }
            }
            System.out.println(ans);
        }
    }
}