38 lines
937 B
C
38 lines
937 B
C
#include "binary_search.h"
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const int *binary_search(int v, const int *a, size_t size)
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{
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size_t lo, hi, i;
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/* early exclude invalid/trivial result: NULL/empty array, value off bounds
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*/
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if (!size || !a || v < *a || v > *(a+size-1))
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return NULL;
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for (lo=0, hi=size-1, i=hi/2; lo<hi && a[i]!=v; i=lo+(hi-lo)/2) {
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if (a[i] < v)
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lo=i+1;
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else
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hi=i-1;
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}
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return a[i]==v? a+i: NULL;
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}
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/* See GNUmakefile below for explanation
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* https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
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*/
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#ifdef UNIT_TEST
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int main(int ac, char **av)
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{
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int arg=1, *res;
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int i, array[] = {1, 2, 3, 4, 6, 7, 8, 9 };
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size_t size = sizeof(array) / sizeof(array[0]);
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for (; arg<ac; ++arg) {
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i=atoi(av[arg]);
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res=binary_search(i, array, size);
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printf("binary_search(%d)=%ld\n", i,
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res? res-array: -1);
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}
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}
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#endif
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