69 lines
2.1 KiB
C
69 lines
2.1 KiB
C
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#ifndef _ROSE_COMPRESSION_BINARY_SEARCH_H__
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#define _ROSE_COMPRESSION_BINARY_SEARCH_H__
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// From wikipedia
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int binary_search(int * A, int value, intptr_t high, intptr_t low) {
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int N = high;
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// low = 0;
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// high = N;
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while (low < high) {
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intptr_t mid = low + ((high - low) / 2);
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if (A[mid] < value)
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low = mid + 1;
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else
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//can't be high = mid-1: here A[mid] >= value,
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//so high can't be < mid if A[mid] == value
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high = mid;
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}
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// high == low, using high or low depends on taste
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if ((low < N) && (A[low] == value))
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return low; // found
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else
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return -1; // not found
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}
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#define rose_binary_search(accessor) do{ \
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int64_t bs_N = bs_high; \
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int64_t bs_mid; \
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while (bs_low < bs_high) { \
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bs_mid = bs_low + ((bs_high - bs_low) / 2); \
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if (*accessor(bs_mid) /*A[mid]*/ < bs_value) \
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bs_low = bs_mid + 1; \
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else \
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/*can't be high = mid-1: here A[mid] >= value,*/ \
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/*so high can't be < mid if A[mid] == value*/ \
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bs_high = bs_mid; \
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} \
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/* high == low, using high or low depends on taste */ \
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if ((bs_low < bs_N) && (*accessor(bs_low)/*A[low]*/ == bs_value)) \
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bs_ret = bs_low; /* found */ \
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else \
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bs_ret = -1; /* not found */ \
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} while(0)
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/** Find the insertion point for a value in the array. Assumes that items stored in the array are unique. */
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#define rose_binary_search_greatest_lower(accessor) do{ \
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int64_t bs_N = bs_high; \
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int64_t bs_mid; \
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while (bs_low < bs_high) { \
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bs_mid = bs_low + ((bs_high - bs_low) / 2); \
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if (accessor(bs_mid) /*A[mid]*/ < bs_value) \
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bs_low = bs_mid + 1; \
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else \
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/*can't be high = mid-1: here A[mid] >= value,*/ \
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/*so high can't be < mid if A[mid] == value*/ \
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bs_high = bs_mid; \
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} \
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/* high == low, using high or low depends on taste */ \
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if ((bs_low < bs_N)) \
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bs_ret = bs_low; /* found */ \
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else \
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bs_ret = -1; /* not found */ \
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} while(0)
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#endif // _ROSE_COMPRESSION_BINARY_SEARCH_H__
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