#include <stdio.h>
#include <stdint.h>
int binary_search(uint8_t *arr, uint8_t n, uint8_t key) {
// Corner case for just one element
if (n == 1) {
if (arr[0] == key) {
return 0;
} else {
return -1;
}
}
// Ceiling operator
int idx = (n+2-1)/2;
while (idx >= 0 && idx <= (n-1)) {
int delta = (n-idx+2-1)/2;
if (arr[idx] == key) {
return idx;
} else if (arr[idx] > key) {
idx -= delta;
} else if (arr[idx] < key) {
idx += delta;
}
}
return -1;
}
int main() {
uint8_t n, key;
scanf("%hhu", &n);
uint8_t arr[100];
for (uint8_t i = 0; i < n; i++) {
scanf("%hhu", &arr[i]);
}
scanf("%hhu", &key);
int index = binary_search(arr, n, key);
printf("%d", index);
return 0;
}
Input
6 5 10 15 20 25 30 20
Expected Output
3