29. Trapping Rain Water
Given bar heights, compute how much rain water can be trapped.
範例 1:
輸入： height = [0,1,0,2,1,0,1,3,2,1,2,1] 輸出： 6
範例 2:
輸入： height = [4,2,0,3,2,5] 輸出： 9
限制條件：
0 <= height.length <= 2 * 10^4
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Given bar heights, compute how much rain water can be trapped.
輸入： height = [0,1,0,2,1,0,1,3,2,1,2,1] 輸出： 6
輸入： height = [4,2,0,3,2,5] 輸出： 9
0 <= height.length <= 2 * 10^4