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49 lines
1.4 KiB
49 lines
1.4 KiB
3 months ago
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/*
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* UCW Library -- Generic Binary Search
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*
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* (c) 2005 Martin Mares <mj@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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/***
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* [[defs]]
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* Definitions
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* -----------
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***/
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/**
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* Find the first element not lower than @x in the sorted array @ary of @N elements (non-decreasing order).
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* Returns the index of the found element or @N if no exists. Uses `ary_lt_x(ary,i,x)` to compare the @i'th element with @x.
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* The time complexity is `O(log(N))`.
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**/
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#define BIN_SEARCH_FIRST_GE_CMP(ary,N,x,ary_lt_x) ({ \
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uint l = 0, r = (N); \
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while (l < r) \
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{ \
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uint m = (l+r)/2; \
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if (ary_lt_x(ary,m,x)) \
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l = m+1; \
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else \
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r = m; \
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} \
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l; \
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})
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/**
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* The default comparision macro for @BIN_SEARCH_FIRST_GE_CMP().
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**/
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#define ARY_LT_NUM(ary,i,x) (ary)[i] < (x)
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/**
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* Same as @BIN_SEARCH_FIRST_GE_CMP(), but uses the default `<` operator for comparisions.
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**/
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#define BIN_SEARCH_FIRST_GE(ary,N,x) BIN_SEARCH_FIRST_GE_CMP(ary,N,x,ARY_LT_NUM)
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/**
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* Search the sorted array @ary of @N elements (non-decreasing) for the first occurence of @x.
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* Returns the index or -1 if no such element exists. Uses the `<` operator for comparisions.
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**/
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#define BIN_SEARCH_EQ(ary,N,x) ({ int i = BIN_SEARCH_FIRST_GE(ary,N,x); if (i >= (N) || (ary)[i] != (x)) i=-1; i; })
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