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"title": "Find the Middle Index in Array",
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"content": "<p>Given a <strong>0-indexed</strong> integer array <code>nums</code>, find the <strong>leftmost</strong> <code>middleIndex</code> (i.e., the smallest amongst all the possible ones).</p>\n\n<p>A <code>middleIndex</code> is an index where <code>nums[0] + nums[1] + ... + nums[middleIndex-1] == nums[middleIndex+1] + nums[middleIndex+2] + ... + nums[nums.length-1]</code>.</p>\n\n<p>If <code>middleIndex == 0</code>, the left side sum is considered to be <code>0</code>. Similarly, if <code>middleIndex == nums.length - 1</code>, the right side sum is considered to be <code>0</code>.</p>\n\n<p>Return <em>the <strong>leftmost</strong> </em><code>middleIndex</code><em> that satisfies the condition, or </em><code>-1</code><em> if there is no such index</em>.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [2,3,-1,<u>8</u>,4]\n<strong>Output:</strong> 3\n<strong>Explanation:</strong> The sum of the numbers before index 3 is: 2 + 3 + -1 = 4\nThe sum of the numbers after index 3 is: 4 = 4\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [1,-1,<u>4</u>]\n<strong>Output:</strong> 2\n<strong>Explanation:</strong> The sum of the numbers before index 2 is: 1 + -1 = 0\nThe sum of the numbers after index 2 is: 0\n</pre>\n\n<p><strong>Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [2,5]\n<strong>Output:</strong> -1\n<strong>Explanation:</strong> There is no valid middleIndex.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= nums.length <= 100</code></li>\n\t<li><code>-1000 <= nums[i] <= 1000</code></li>\n</ul>\n\n<p> </p>\n<p><strong>Note:</strong> This question is the same as 724: <a href=\"https://leetcode.com/problems/find-pivot-index/\" target=\"_blank\">https://leetcode.com/problems/find-pivot-index/</a></p>\n",
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"code": "class Solution {\npublic:\n int findMiddleIndex(vector<int>& nums) {\n \n }\n};",
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"hints": [
"Could we go from left to right and check to see if an index is a middle index?",
"Do we need to sum every number to the left and right of an index each time?",
"Use a prefix sum array where prefix[i] = nums[0] + nums[1] + ... + nums[i]."
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