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In computer science, the all nearest smaller values problem is the following task: for each position in a sequence of numbers, search among the previous positions for the last position that contains a smaller value. This problem can be solved efficiently both by parallel and non-parallel algorithms: , who first identified the procedure as a useful subroutine for other parallel programs, developed efficient algorithms to solve it in the Parallel Random Access Machine model; it may also be solved in linear time on a non-parallel computer using a stack-based algorithm. Later researchers have studied algorithms to solve it in other models of parallel computation. ==Example== Suppose that the input is the binary van der Corput sequence :0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15. The first element of the sequence (0) has no previous value. The nearest (only) smaller value previous to 8 and to 4 is 0. All three values previous to 12 are smaller, but the nearest one is 4. Continuing in the same way, the nearest previous smaller values for this sequence (indicating the nonexistence of a previous smaller value by a dash) are :—, 0, 0, 4, 0, 2, 2, 6, 0, 1, 1, 5, 1, 3, 3, 7. In most applications, the positions of the nearest smaller values, and not the values themselves, should be computed, and in many applications the same computation should be computed for the reversal of the sequence in order to find the following smaller value that is closest in the sequence. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「All nearest smaller values」の詳細全文を読む スポンサード リンク
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