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this a sorting algorithm that is suitable for sorting lists of elements where the number of elements and the number of possible key values are approximately the same. It requires O(n + Range) time where n is number of elements in input array and ‘Range’ is number of possible values in array.
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#include <bits/stdc++.h> | ||
using namespace std; | ||
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/* Sorts the array using pigeonhole algorithm */ | ||
void pigeonholeSort(int arr[], int n) | ||
{ | ||
// Find minimum and maximum values in arr[] | ||
int min = arr[0], max = arr[0]; | ||
for (int i = 1; i < n; i++) | ||
{ | ||
if (arr[i] < min) | ||
min = arr[i]; | ||
if (arr[i] > max) | ||
max = arr[i]; | ||
} | ||
int range = max - min + 1; // Find range | ||
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// Create an array of vectors. Size of array | ||
// range. Each vector represents a hole that | ||
// is going to contain matching elements. | ||
vector<int> holes[range]; | ||
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// Traverse through input array and put every | ||
// element in its respective hole | ||
for (int i = 0; i < n; i++) | ||
holes[arr[i]-min].push_back(arr[i]); | ||
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// Traverse through all holes one by one. For | ||
// every hole, take its elements and put in | ||
// array. | ||
int index = 0; // index in sorted array | ||
for (int i = 0; i < range; i++) | ||
{ | ||
vector<int>::iterator it; | ||
for (it = holes[i].begin(); it != holes[i].end(); ++it) | ||
arr[index++] = *it; | ||
} | ||
} | ||
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// Driver program to test the above function | ||
int main() | ||
{ | ||
int arr[] = {8, 3, 2, 7, 4, 6, 8}; | ||
int n = sizeof(arr)/sizeof(arr[0]); | ||
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pigeonholeSort(arr, n); | ||
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printf("Sorted order is : "); | ||
for (int i = 0; i < n; i++) | ||
printf("%d ", arr[i]); | ||
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return 0; | ||
} |