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41 lines
1.5 KiB
HTML
41 lines
1.5 KiB
HTML
<p>You are given an integer array <code>nums</code> and an integer <code>target</code>.</p>
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<p>You want to build an <strong>expression</strong> out of nums by adding one of the symbols <code>'+'</code> and <code>'-'</code> before each integer in nums and then concatenate all the integers.</p>
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<ul>
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<li>For example, if <code>nums = [2, 1]</code>, you can add a <code>'+'</code> before <code>2</code> and a <code>'-'</code> before <code>1</code> and concatenate them to build the expression <code>"+2-1"</code>.</li>
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</ul>
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<p>Return the number of different <strong>expressions</strong> that you can build, which evaluates to <code>target</code>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> nums = [1,1,1,1,1], target = 3
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<strong>Output:</strong> 5
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<strong>Explanation:</strong> There are 5 ways to assign symbols to make the sum of nums be target 3.
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-1 + 1 + 1 + 1 + 1 = 3
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+1 - 1 + 1 + 1 + 1 = 3
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+1 + 1 - 1 + 1 + 1 = 3
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+1 + 1 + 1 - 1 + 1 = 3
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+1 + 1 + 1 + 1 - 1 = 3
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> nums = [1], target = 1
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<strong>Output:</strong> 1
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= nums.length <= 20</code></li>
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<li><code>0 <= nums[i] <= 1000</code></li>
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<li><code>0 <= sum(nums[i]) <= 1000</code></li>
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<li><code>-1000 <= target <= 1000</code></li>
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</ul>
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