{ "data": { "question": { "questionId": "282", "questionFrontendId": "282", "boundTopicId": null, "title": "Expression Add Operators", "titleSlug": "expression-add-operators", "content": "

Given a string num that contains only digits and an integer target, return all possibilities to insert the binary operators '+', '-', and/or '*' between the digits of num so that the resultant expression evaluates to the target value.

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Note that operands in the returned expressions should not contain leading zeros.

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Example 1:

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\nInput: num = "123", target = 6\nOutput: ["1*2*3","1+2+3"]\nExplanation: Both "1*2*3" and "1+2+3" evaluate to 6.\n
\n\n

Example 2:

\n\n
\nInput: num = "232", target = 8\nOutput: ["2*3+2","2+3*2"]\nExplanation: Both "2*3+2" and "2+3*2" evaluate to 8.\n
\n\n

Example 3:

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\nInput: num = "3456237490", target = 9191\nOutput: []\nExplanation: There are no expressions that can be created from "3456237490" to evaluate to 9191.\n
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Constraints:

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Can we keep track of the expression's value as well so as to avoid the evaluation at the very end of recursion?", "Think carefully about the multiply operator. It has a higher precedence than the addition and subtraction operators. \r\n\r\n
1 + 2 = 3
\r\n1 + 2 - 4 --> 3 - 4 --> -1
\r\n1 + 2 - 4 * 12 --> -1 * 12 --> -12 (WRONG!)
\r\n1 + 2 - 4 * 12 --> -1 - (-4) + (-4 * 12) --> 3 + (-48) --> -45 (CORRECT!)", "We simply need to keep track of the last operand in our expression and reverse it's effect on the expression's value while considering the multiply operator." ], "solution": { "id": "548", "canSeeDetail": true, "paidOnly": false, "hasVideoSolution": false, "paidOnlyVideo": true, "__typename": "ArticleNode" }, "status": null, "sampleTestCase": "\"123\"\n6", "metaData": "{\r\n \"name\":\"addOperators\",\r\n \"params\":[\r\n {\r\n \"name\":\"num\",\r\n \"type\":\"string\"\r\n },\r\n {\r\n \"name\":\"target\",\r\n \"type\":\"integer\"\r\n }\r\n ],\r\n \"return\":{\r\n \"type\":\"list\"\r\n }\r\n}", "judgerAvailable": true, "judgeType": "large", "mysqlSchemas": [], "enableRunCode": true, "enableTestMode": false, "enableDebugger": true, "envInfo": "{\"cpp\": [\"C++\", \"

Compiled with clang 11 using the latest C++ 20 standard.

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Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.

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Most standard library headers are already included automatically for your convenience.

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Python 2.7.12.

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C# 10 with .NET 6 runtime

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Node.js 16.13.2.

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Ruby 3.1

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Go 1.21

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Python 3.10.

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