确定性算法A查找链表中的x下标

ch11.ppt P59 


#include "pch.h"
#include <iostream>
#include <random>
#include <vector>
#include <ctime>
#include <algorithm>
#define MAXN 10000
using namespace std;
//产生一个随机数组val
vector<int> getVector() {
	vector<int> v;
	uniform_int_distribution<unsigned> u(1, 1000);
	default_random_engine e(time(0));
	for (auto i = 1; i <=10; ++i)
		v.push_back(u(e));
	return v;

}
//打印数组
void print(vector<int> v) {
	for (auto i : v)
		cout << i << " ";
	cout << endl;
}
//生成数组ptr[]
vector<int> getPtr(vector<int> val) {
	vector<int> ptr(val.size(),-1);
	auto min_it = min_element(val.begin(), val.end());
	int pos = min_it-val.begin();
	int head = pos;
	while (*min_it != MAXN) {
		*min_it = MAXN;
		
		pos = min_it - val.begin();
		
		min_it = min_element(val.begin(), val.end());

		ptr[pos] = min_it - val.begin();
		
	}
	ptr[pos] = head;
	return ptr;
}
//查找x在数组val的下标
int Search(int x, int i,vector<int> val,vector<int> ptr) {
	while (x > val[i])
		i = ptr[i];
	return i;
}
//算法A(x),在表val中查找x的下标
int A(int x, vector<int> val, vector<int> ptr) {
	int head = min_element(val.begin(), val.end()) - val.begin();
	return Search(x, head, val, ptr);
}
int main() {
	vector<int> val = {2,3,13,1,5,21,8};
	
	vector<int> ptr = getPtr(val);
	print(val);

	cout << A(8, val, ptr) << endl;

}

 

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