How to design priority for operational expressions in big data
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Given a string containing numbers and operators, add parentheses to the expression and change its priority to get different results. You need to give the results of all possible combinations. Valid operation symbols include +, -, and *.
Example 1:
Input: output: explanation: (2-1)-1) = 0 (2-(1-1)) = 2
Example 2:
Input: "2: 3-4: 5" output: [- 34,-14,-10,-10] explain: (2 * (3-(4-5) =-34
Answer:
1public List diffWaysToCompute (String input) {
2 List res = new ArrayList ()
3 for (int I = 0; I < input.length (); iTunes +) {
4 char c = input.charAt (I)
5 if (c = ='-'| | c = ='+'| | c = ='*') {
6 String a = input.substring (0, I)
7 String b = input.substring (I + 1)
8 List al = diffWaysToCompute (a)
9 List bl = diffWaysToCompute (b)
10 for (int x: al) {
11 for (int y: bl) {
12 if (c = ='-') {
13 res.add (x-y)
14} else if (c ='+') {
15 res.add (x + y)
16} else if (c ='*') {
17 res.add (x * y)
18}
19}
20}
21}
22}
23 if (res.size () = = 0)
24 res.add (Integer.valueOf (input))
25 return res
26}
Parsing:
First, the string is intercepted, and then the calculated value is added, subtracted and multiplied by recursion. Notice lines 23 through 24. When truncating the head and tail numbers respectively, res may be empty, so you need to add the input value to the res collection.
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