{leetcode}/problems/the-score-of-students-solving-math-expression/[LeetCode - 2019. The Score of Students Solving Math Expression ^]
You are given a string s
that contains digits 0-9
, addition symbols '+'
, and multiplication symbols ''
*only, representing a valid math expression of single digit numbers (e.g., 3+5*2
). This expression was given to n
elementary school students. The students were instructed to get the answer of the expression by following this order of operations:
-
Compute multiplication, reading from left to right; Then,
-
Compute addition, reading from left to right.
You are given an integer array answers
of length n
, which are the submitted answers of the students in no particular order. You are asked to grade the answers
, by following these rules:
-
If an answer equals the correct answer of the expression, this student will be rewarded
5
points; -
Otherwise, if the answer could be interpreted as if the student applied the operators in the wrong order but had correct arithmetic, this student will be rewarded
2
points; -
Otherwise, this student will be rewarded
0
points.
Return the sum of the points of the students.
Example 1: <img alt="" src="https://assets.leetcode.com/uploads/2021/09/17/student_solving_math.png" style="width: 678px; height: 109px;" />
Input: s = "7+3*1*2", answers = [20,13,42] Output: 7 Explanation: As illustrated above, the correct answer of the expression is 13, therefore one student is rewarded 5 points: 13,42] A student might have applied the operators in this wrong order: ((7+3)1)*2 = 20. Therefore one student is rewarded 2 points: *20,13,42] The points for the students are: [2,5,0]. The sum of the points is 2+5+0=7.
Example 2:
Input: s = "3+5*2", answers = [13,0,10,13,13,16,16] Output: 19 Explanation: The correct answer of the expression is 13, therefore three students are rewarded 5 points each: 13,0,10,13,13,16,16] A student might have applied the operators in this wrong order: ((3+5)2 = 16. Therefore two students are rewarded 2 points: 16,16*] The points for the students are: [5,0,0,5,5,2,2]. The sum of the points is 5+0+0+5+5+2+2=19.
Example 3:
Input: s = "6+0*1", answers = [12,9,6,4,8,6] Output: 10 Explanation: The correct answer of the expression is 6. If a student had incorrectly done (6+0)*1, the answer would also be 6. By the rules of grading, the students will still be rewarded 5 points (as they got the correct answer), not 2 points. The points for the students are: [0,0,5,0,0,5]. The sum of the points is 10.
Constraints:
-
3 ⇐ s.length ⇐ 31
-
s
represents a valid expression that contains only digits0-9
,'+'
, and'*'
only. -
All the integer operands in the expression are in the inclusive range
[0, 9]
. -
1 ⇐
The count of all operators ('+'
and'*'
) in the math expression⇐ 15
-
Test data are generated such that the correct answer of the expression is in the range of
[0, 1000]
. -
n == answers.length
-
1 ⇐ n ⇐ 104
-
0 ⇐ answers[i] ⇐ 1000