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binarySearch.cpp
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55 lines (47 loc) · 1.1 KB
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#include <queue>
#include <vector>
using namespace std;
/* Recursive */
int binarySearch(vector<int>& arr, int target, int start, int end) {
if (start > end) return -1;
int mid = (start + end) / 2;
if (arr[mid] == target)
return mid; // if find
else if (arr[mid] > target)
return binarySearch(arr, target, start, mid - 1);
else
return binarySearch(arr, target, mid + 1, end);
}
/* Loop */
int binarySearch(vector<int>& arr, int target, int start, int end) {
while (start <= end) {
int mid = (start + end) / 2;
if (arr[mid] == target)
return mid;
else if (arr[mid] > target)
end = mid + 1;
else
start = mid + 1;
}
return -1;
}
int lower_bound(int arr[], int target, int size){
int mid, start, end;
start = 0, end = size-1;
while (start < end){
mid = (start + end) / 2;
if (target <= arr[mid]) end = mid;
else start = mid + 1;
}
return end;
}
int upper_bound(int arr[], int target, int size){
int mid, start, end;
start = 0, end = size - 1;
while (start < end) {
mid = (start + end) / 2;
if (target < arr[mid]) end = mid;
else start = mid + 1;
}
return end;
}