54 lines
1.2 KiB
C++
54 lines
1.2 KiB
C++
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/* Dutch Flag Algo: To separate three different entities
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e.g :- Sort 0s,1s and 2s in an array without using sorting algo
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Complexity : O(n)
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*/
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#include <iostream>
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using namespace std;
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/* 0 0 0 1 1 1 ? ? ? ? 2 2 2
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v v v
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Low Mid High
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> In this algo, we tend to shrink this '?' region
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whose ends are pointed by Mid and High indexes.
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> Low points to the region where the 1s start
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*/
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void dutch_flag(int arr[],int size){
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//mid to high is the region we are about to shrink
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int low = 0, mid = 0, high = size-1;
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while(mid <= high){
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if(arr[mid] == 0){
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swap(arr[low],arr[mid]);
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low++; mid++;
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}
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else if(arr[mid] == 1){
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mid++;
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}
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else if(arr[mid] == 2){
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swap(arr[high],arr[mid]);
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high--;
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}
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}
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}
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//Utility function to print the array
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void printArray(int arr[], int arr_size)
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{
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for (int i = 0; i < arr_size; i++)
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cout << arr[i] << " ";
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}
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int main(){
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int a[] = {0, 1, 1, 0, 1, 2, 1, 2, 0, 0, 0, 1};
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int n = sizeof(a)/sizeof(a[0]);
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dutch_flag(a,n);
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printArray(a,n);
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return 0;
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}
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