題目:給定一個數組和滑動窗日的大小,請找出所有滑動窗口裏的最大值。如果輸入數組{2,3,4,2,6,2,5,1}及滑動窗印的大小3,那麼存在6個滑動窗口,它們的最大值分別爲{4,4,6,6,6,5}。
第一想法是按窗口滑動,每次對比窗口內的數字大小,選出最大值,但很明顯,這裏存在着很多次重複的大小對比操作,將那些重複的操作想辦法剪去即可。
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
vector<int> maxnum_in_window(const vector<int>& data, unsigned int windowsize)
{
vector<int> maxnum;
if (windowsize <= data.size() && windowsize >= 1){
deque<int> index;
for (unsigned int i = 0; i < windowsize; ++i){
while (!index.empty() && data[i] >= data[index.back()])
index.pop_back();
index.push_back(i);
}
for (unsigned int i = windowsize; i < data.size(); ++i){
maxnum.push_back(data[index.front()]);
while (!index.empty() && data[i] >= data[index.back()])
index.pop_back();
if (!index.empty() && index.front() <= (i - windowsize))
index.pop_front();
index.push_back(i);
}
maxnum.push_back(data[index.front()]);
}
return maxnum;
}
void test(char* testname, vector<int>& T, unsigned int windowsize)
{
cout << endl << "----" << testname << "----" << endl;
vector<int> maxnum = maxnum_in_window(T, windowsize);
for (unsigned int i = 0; i < maxnum.size(); ++i){
cout << maxnum[i] << ",";
}
}
void test1()
{
vector<int> T1 = { 2, 3, 4, 2, 6, 2, 5, 1 };
unsigned int windowsize = 3;
test("test1", T1, windowsize);
}
int main(int argc, char* argv[])
{
test1();
system("pause");
return 0;
}