HackerRank - Find Maximum Index Product

最新推荐文章于 2019-05-19 23:16:47 发布

转载最新推荐文章于 2019-05-19 23:16:47 发布 · 142 阅读

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原文链接：http://www.cnblogs.com/tonix/p/4492195.html

本文介绍了一种解决Hackerrank平台上的最大索引乘积问题的优化算法，通过使用C++实现，重点在于理解并优化数据结构和算法效率。

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I treated it too difficult.. nothing special, just some optimization mentioned as:

http://saraguru.weebly.com/how-i-solved/find-maximum-index-product-hackerrank

#include <cmath>
#include <cstdio>
#include <vector>
#include <map>
#include <set>
#include <unordered_set>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
    int n; cin >> n;
    vector<int> in;
    for (int i = 0; i < n; i++)
    {
        int tmp; cin >> tmp;
        in.push_back(tmp);
    }

    vector<int> left(n, 0);
    for (int i = 1; i < n; i++)
    {
        if (in[i] == in[i-1])
        {
            left[i] = left[i - 1];
        }
        else if (in[i] < in[i - 1])
        {
            left[i] = i;
        }
        else if (in[i] > in[i - 1])
        {
            int j = left[i - 1];
            while (j >= 0)
            {
                if (in[j] > in[i])
                {
                    left[i] = j + 1;
                    break;
                }
                j--;
            }
        }
    }

    vector<int> right(n, 0);
    for (int i = n - 2; i >= 0; i--)
    {

        if (in[i] == in[i + 1])
        {
            right[i] = right[i + 1];
        }
        else if (in[i] < in[i + 1])
        {
            right[i] = i + 1 + 1;
        }
        else if (in[i] > in[i + 1])
        {
            int j = right[i + 1];
            while (j < n)
            {
                if (in[j] > in[i])
                {
                    right[i] = j + 1;
                    break;
                }
                j++;
            }
        }
    }

    //    get
    long long ret = 0;
    for (int i = 1; i < n - 1; i++)
    {
        ret = std::max(ret, (long long)left[i] * (long long)right[i]);
    }
    cout << ret << endl;
    return 0;
}