2020_12_2_数据结构

#include <bits/stdc++.h>
using namespace std;

const int maxn = 1e7;
int a[maxn];
int t[maxn];

void sort(int n)
{
	int maxnum = 0;
	for(int i = 0; i < n; i++){
		t[a[i]]++;
		if( a[i] > maxnum ) maxnum = a[i];
	}

	int cnt = 0;
	for(int i = 0; i <= maxnum; i++){

		if(t[i] != 0)
		for(int j =0 ; j < t[i]; j++)
			a[cnt++] = i;
	}

	for(int i = 0 ;i < n ; i++){
		cout << a[i] << " ";
	}
	cout << endl;
}

int lower_Find(int n , int x)
{
    int l = 0 , r = n;
    while(l < r)
    {
        int mid = (l + r) >> 1;
        if(a[mid] < x) l = mid + 1;
        else r = mid;
    }

    return r;
}

int upper_Find(int n ,int x)
{
    int l = 0 ,r = n;
    while(l < r)
    {
        int mid = (l + r + 1) >> 1;
        if( a[mid] <= x ) l = mid ;
        else r = mid - 1;
    }
    return r;
}

int main()
{
	int n;
    cout << "请输入需要创建的数组大小： " << endl;
	cin >> n;

	memset(t,0,sizeof t);

	srand( (unsigned int) time(NULL) );
	for(int i = 0; i < n ; i++){
		a[i] = rand()%10;
	}

	sort(n);

    int x;
    cout << "请输入要查找的数据" << endl;
    cin >> x;
    cout << "如果是找这个数第一次出现的位置输入1 " <<endl;
    cout << "如果是找这个数最后一次出现的位置输入2 " <<endl;
    int fx,cmd;
    cin >> cmd
    if(cmd  == 1)
        fx = lower_Find(n,x);
    else if (cmd == 2)
        fx = upper_Find(n,x);

    if( a[fx] == x) cout << "找到 " << x << " 在第 " << fx+1 << " 位"<< endl;
    else cout << "没有找到这个数" << endl;
	return 0;
}