【菜鸟er】搜索专题_优化线性搜索

最新推荐文章于 2021-11-07 01:05:34 发布

mmciel

最新推荐文章于 2021-11-07 01:05:34 发布

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本文通过三种不同的线性搜索实现方式，对搜索效率进行了对比测试。使用C++编写了简单的线性搜索算法，并通过时间记录函数测量不同方法的运行时间，结果显示在小规模数据集上各种方法的时间差异不明显。

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#include <bits/stdc++.h>
#include <time.h>
using namespace std;
#define N 1000

template<typename T>
int line_search(T a[],T flagnum, T n)
{
    int i = 0;
	a[n] = flagnum;
	while(a[i] != flagnum)
		i++;
    return i;//返回搜索结果的下标
}

int main()
{
	int n = 153;
	int a[N]= {684,435,237,140,475,585,249,738,437,541,
			940,343,514,362,629,466,582,641,314,59,
			982,166,450,314,595,703,436,795,148,17,
			684,435,237,140,475,585,249,738,437,541,
			940,343,514,362,629,466,582,641,314,59,
			982,166,450,314,595,703,436,795,148,17,
			684,435,237,140,475,585,249,738,437,541,
			940,343,514,362,629,466,582,641,314,59,
			982,166,450,314,595,703,436,795,148,17,
			684,435,237,140,475,585,249,738,437,541,
			940,343,514,362,629,466,582,641,314,59,
			982,166,450,314,595,703,436,795,148,17,
			684,435,237,140,475,585,249,738,437,541,
			940,343,514,362,629,466,582,641,314,59,
			982,166,450,314,595,703,436,795,148,17,77777,88767,66666};
	int flagnum=88767;
	//one:
    cout<<"1:"<<endl;
	clock_t time1 = clock();

	int k=n+1;
	for(int i=0;i<n;i++){
		if(a[i] == flagnum){
			k=i;
			break;
		}
	}
	if(a[k]!=flagnum)
		cout<<"NO"<<endl;
	else cout<<k<<endl;

	clock_t time2 = clock();

	cout <<"Running Time == "<<(double)(time2 - time1) / CLOCKS_PER_SEC << endl;

	//two:
	cout<<"2:"<<endl;
	clock_t time3= clock();

	int i = 0;
	a[n] = flagnum;//制定终止条件 防止无限循环
	while(a[i] != flagnum)
		i++;
	if(i==n)
		cout<<"NO"<<endl;
	else cout<<k<<endl;

    clock_t time4 = clock();
    cout <<"Running Time == "<<(double)(time4 - time3) / CLOCKS_PER_SEC << endl;

    //three:
	cout<<"3:"<<endl;
	clock_t time5= clock();

    int i2 = line_search(a,flagnum,n);
	if(i2==n)
		cout<<"NO"<<endl;
	else cout<<k<<endl;

    clock_t time6 = clock();
    cout <<"Running Time == "<<(double)(time6 - time5) / CLOCKS_PER_SEC << endl;

	return 0;
}
/**
//数据规模小，无法比较1,2的差距。
1:
151
Running Time == 0
2:
151
Running Time == 0
3:
151
Running Time == 0.001
*/