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maximumDifference.cpp
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94 lines (82 loc) · 2.89 KB
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#include <iostream>
#include <vector>
#include <algorithm>
#include <random>
#include <chrono>
// Given a 0-indexed integer array nums of size n,
// find the maximum difference between nums[i] and nums[j]
// (i.e., nums[j] - nums[i]), such that 0 <= i < j < n and nums[i] < nums[j].
// using Kadane's Algorithm
class Solution {
public:
int maximumDifference(const std::vector<int>& nums) {
int currentMax {0};
int resultMax {-1};
for (size_t i {0}; i < nums.size()-1; i++) {
int diff = nums[i+1]-nums[i];
if (diff == 0) continue;
currentMax = std::max(diff + currentMax, diff);
resultMax = std::max(resultMax, currentMax);
}
return resultMax < 0 ? -1 : resultMax;
}
};
template <
class result_t = std::chrono::microseconds,
class clock_t = std::chrono::steady_clock,
class duration_t = std::chrono::milliseconds
>
auto since(std::chrono::time_point<clock_t, duration_t> const& start)
{
return std::chrono::duration_cast<result_t>(clock_t::now() - start);
}
int main()
{
// test with small data set
std::vector<int> vec { 1, 3, 4, 6, 2, 5};
std::cout << "Maximum difference is " << Solution().maximumDifference(vec);
std::cout<<std::endl;
// generate vector with 0 - 9999
std::vector<int> v;
for(int i{1}; i<10000; i++)
{
v.push_back(i);
}
// shffle generated vector
auto rng {std::default_random_engine {}};
std::shuffle(std::begin(v), std::end(v), rng);
// with kadane's algorithm o(n)
auto start {std::chrono::steady_clock::now()};
int resKadane = Solution().maximumDifference(v);
auto passedTime {since(start).count()};
std::cout << "Maximum difference is with kadane's algorithm ";
std::cout << resKadane <<std::endl;
std::cout << "Elapsed(us)=" << passedTime << std::endl;
std::cout<<std::endl;
// with sort (nlogn)
std::vector<int> vecCopy = v;
int resultSort {0};
start = std::chrono::steady_clock::now();
std::sort(vecCopy.begin(), vecCopy.end());
resultSort = vecCopy[vecCopy.size()-1] - vecCopy[0];
passedTime = since(start).count();
std::cout << "Maximum difference is with sort ";
std::cout<<resultSort<<std::endl;
std::cout << "Elapsed(us)=" << passedTime << std::endl;
std::cout<<std::endl;
// with (n2)
int result {0};
start = std::chrono::steady_clock::now();
for(size_t i{0}; i<v.size(); i++)
{
for(size_t j{0}; j<v.size(); j++)
{
result = std::max(result, v[j] - v[i]);
}
}
passedTime = since(start).count();
std::cout << "Maximum difference is with n2 ";
std::cout<<result<<std::endl;
std::cout << "Elapsed(us)=" << passedTime << std::endl;
return 0;
}