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Binary Search in C++
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#include <iostream> | |
/* Binary Search */ | |
int binarySearch(int *array, int n, int target) | |
{ | |
int low = 0; | |
int high = n - 1; | |
while (low <= high) | |
{ | |
int middle = (low + high) / 2; | |
if (array[middle] == target) | |
return middle; | |
else if (array[middle] < target) | |
low = middle + 1; | |
else | |
high = middle - 1; | |
} | |
return -1; | |
} | |
/* Binary Search finding the first occurence of target */ | |
int binarySearchFirst(int *array, int n, int target) | |
{ | |
int low = 0; | |
int high = n - 1; | |
int first = -1; | |
while (low <= high) | |
{ | |
int middle = (low + high) / 2; | |
if (array[middle] == target) | |
{ | |
first = middle; | |
high = middle - 1; | |
} | |
else if (array[middle] < target) | |
low = middle + 1; | |
else | |
high = middle - 1; | |
} | |
return first; | |
} | |
/* Binary Search finding the last occurence of target */ | |
int binarySearchLast(int *array, int n, int target) | |
{ | |
int low = 0; | |
int high = n - 1; | |
int last = -1; | |
while (low <= high) | |
{ | |
int middle = (low + high) / 2; | |
if (array[middle] == target) | |
{ | |
last = middle; | |
low = middle + 1; | |
} | |
else if (array[middle] < target) | |
low = middle + 1; | |
else | |
high = middle - 1; | |
} | |
return last; | |
} | |
int main() | |
{ | |
/* Sorted array containing duplicate values */ | |
int array[] = {1, 5, 12, 48, 49, 49, 49, 50, 50, 65, 89}; | |
int n = sizeof(array)/sizeof(array[0]); | |
/* Regular Binary Search */ | |
std::cout << "Value found at Index: " << binarySearch(array, n, 65) << std::endl; | |
/* Binary Search finding first occurence of duplicate values */ | |
std::cout << "Value found at first Index: " << binarySearchFirst(array, n, 49) << std::endl; | |
/* Binary Search finding last occurence of duplicate values */ | |
std::cout << "Value found at last Index: " << binarySearchLast(array, n, 49) << std::endl; | |
return 0; | |
} |
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