求数组中最大的异或值 20171013

最新推荐文章于 2025-05-20 03:30:00 发布

博良仔

最新推荐文章于 2025-05-20 03:30:00 发布

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本文链接：https://blog.youkuaiyun.com/u012136352/article/details/78239881

本文介绍了一种寻找整数序列中连续子序列的最大幸运数的算法。幸运数定义为序列中最大与次大元素的异或值。文章通过示例说明了如何利用栈和双端队列实现该算法，并提供了Python及C++代码实现。

Suppose you have an integer sequence, we define a lucky number as a special integer which is the XOR value of the sequence’s greatest and strict second greatest element. For example, in [1,2,3,3], 3 is the greatest element and 2 is the strict second greatest one, even though we have two 3 at the same time; so the lucky number is 2 xor 3 = 1.
Now given an N-length integer sequence, please find out the maximum lucky number of all continuous subsequences.

输入描述：
The first line is an integer n, representing the length of the value of V[i](1 <= V[i] <= 10^8) in the sequence respectively. We’ll ensure that there are at least two different values from V[1] to V[n. Define the continuous subsequence as [V[1],V[l+1],V[l+2], … ,V[r]] ( 1 <= l <= r <= n)
30% small input: 2 <= n <= 10
40% medium input: 2 <= n <= 5000
30% large input: 2 <= n <= 100000

输出描述：
Output the greatest lucky number

示例1：

输入
5
5 2 1 4 3

输出
7

python代码

array_length = raw_input()
array = raw_input()
num = [int(n) for n in array.split()]

q = []

ans = -999
for value in num:
    while q and q[-1] <= value:#最大的情况
        ans = max(ans,q[-1]^value)
        q.pop()
    if q:#次大的情况
        ans = max(ans,q[-1]^value)
    q.append(value)
print ans

c++代码

#include<iostream>
#include<stdio.h>
#include<deque>
using namespace std;
deque<int>q;
int main(){
    int i, x, ans = -999,n;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&x);
        while(!q.empty()&&q.back()<=x)
        {
            ans = max(ans,q.back()^x);
            q.pop_back();
        }
        if(q.size()>1) ans= max(ans,q.back()^x);
        q.push_back(x);
    }
    printf("%d",ans);
}