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binary search in c

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Wei Yang 2018-10-26 15:26:40 +08:00
parent c2e136f3d8
commit a67fb10a7b
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c-cpp/15_bsearch/binary_search.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
typedef int(*bs)(int *arr, int size, int val);
int binary_search_r(int *arr, int size, int val)
{
int mid = size / 2;
int idx;
if (arr[mid] == val)
return mid;
// mid == 0 means size == 1
// so the only element in array doesn't equal to val
if (!mid)
return -1;
if (arr[mid] < val) {
idx = binary_search_r(arr + mid + 1, size - mid - 1, val);
if (idx != -1)
idx += mid + 1;
} else {
idx = binary_search_r(arr, mid, val);
}
return idx;
}
int binary_search_i(int *arr, int size, int val)
{
int low = 0, high = size - 1, mid;
while (low <= high) {
mid = (low + high) / 2;
if (arr[mid] == val)
return mid;
if (arr[mid] < val)
low = mid + 1;
else
high = mid - 1;
}
return -1;
}
void iteratioin_test(bs binary_search)
{
int arr[10] = {1, 4, 5, 9, 12, 19, 21, 28, 31, 36};
int idx;
idx = binary_search(arr, 10, 12);
if (idx != -1)
printf("find 12 at %d\n", idx);
else
printf("12 not in arr \n");
idx = binary_search(arr, 10, 13);
if (idx != -1)
printf("find 13 at %d\n", idx);
else
printf("13 not in arr \n");
idx = binary_search(arr, 10, 1);
if (idx != -1)
printf("find 1 at %d\n", idx);
else
printf("1 not in arr \n");
idx = binary_search(arr, 10, 36);
if (idx != -1)
printf("find 36 at %d\n", idx);
else
printf("36 not in arr \n");
idx = binary_search(arr, 10, 31);
if (idx != -1)
printf("find 31 at %d\n", idx);
else
printf("31 not in arr \n");
}
int main()
{
printf("=== Test iteration version:\n");
iteratioin_test(binary_search_i);
printf("=== Test recursive version:\n");
iteratioin_test(binary_search_r);
return 0;
}