{ "data": { "question": { "questionId": "407", "questionFrontendId": "407", "boundTopicId": null, "title": "Trapping Rain Water II", "titleSlug": "trapping-rain-water-ii", "content": "

Given an m x n integer matrix heightMap representing the height of each unit cell in a 2D elevation map, return the volume of water it can trap after raining.

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Example 1:

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\nInput: heightMap = [[1,4,3,1,3,2],[3,2,1,3,2,4],[2,3,3,2,3,1]]\nOutput: 4\nExplanation: After the rain, water is trapped between the blocks.\nWe have two small ponds 1 and 3 units trapped.\nThe total volume of water trapped is 4.\n
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Example 2:

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\nInput: heightMap = [[3,3,3,3,3],[3,2,2,2,3],[3,2,1,2,3],[3,2,2,2,3],[3,3,3,3,3]]\nOutput: 10\n
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Constraints:

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