Basic ideas of the drawing algorithm

The lottery is the folk custom of China, which is one of the forms of divination. Then, the form of a lottery can be randomly identified in the sequence. If the luck is good enough, then no matter how much element, it only needs to be aligned once, this is the most mysterious place of this algorithm, and looks with Yang Shou.

step

1. Generate a random number r a n d N u m randNum randNum
2. Random number pairs of array lengths After obtaining the subscript of the pumping element i n d e x = r a n d N u m index=randNum%length index=randNum
3. Compare the target elements, if not, repeat 1, 2; until found

Process demonstration

In the sequence [ 3 , 44 , 38 , 5 , 47 , 15 , 36 , 26 , 1 , 2 ] [3,44,38,5,47,15,36,26,1,2] [3,44,38,5,47,15,36,26,1,2] Find 2

1. First result: Find 1 time

   

2. The second result: Find 18 times

   

3. The third result: Find 3 times

   

Algorithm code

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

// Dump algorithm 
void DrawAlgorithm(int nums[],int num,int n){
	 SRAND ((int) time (0)); // Generate random seeds 
	int count=0,randNum,bound=n*n;		
	 While (True && Count <bound) {// Stop when the number of findings arrive in Bound 
		count++;
		 RandNum = rand ()% n; // Generate random number 
		if(nums[randNum]==num){			
			 Break; // If you find Num, Break exits the loop. 
		}
	}
	 Cout << "has found" << Num << ", looking for count:" << count;
} 

 // Print an array 
void printNum(int numbers[],int n){
	for(int i=0;i<n;i++){
		cout<<numbers[i]<<" ";
	}
	cout<<endl; 
}

int main()
{
	int numbers[10]={3,44,38,5,47,15,36,26,1,2};
	 INT n = sizeof (numbers) / sizeof (NumBers [0]); // array length 
	 Cout << "sequence is:"; 
	 Printnum (NumBers, N); // Print an array 
	 Drawalgorithm (NumBers, 2, N); // Call the DrawAlgorithm function to perform a lottery in the NumBers sequence 2 
    return 0;
}

Algorithm performance analysis

• Spatial complexity: O ( 1 ) O(1) O(1)
• Time complexity
  • Preferably, the time complexity: O ( 1 ) O(1) O(1)
  • Worst cases of time complexity: uncertain