[线段树][ZZNUOJ]易水寒

没必要用线段树

只是想练习一下

#pragma GCC optimize(2)
#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <string>
#include <cstring>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <ctime>
#include <vector>
#include <fstream>
#include <list>
#include <iomanip>
#include <numeric>
using namespace std;
typedef long long ll;

const int MAXN = 1e6 + 100;

ll arr[MAXN] = {0};

ll tree[MAXN * 4 + 10] = {0};

void buildtree(int now, int l, int r)
{
	if(l == r)
	{
		tree[now] = arr[l];
		return ;
	}

	int mid = l + (r - l) / 2;

	buildtree(now * 2, l, mid);

	buildtree(now * 2 + 1, mid + 1, r);

	tree[now] = max(tree[now * 2], tree[now * 2 + 1] );

}

ll find(int now, int l, int r, int x, int y)
{
	if(r < x || l > y)
		return -1;
	if(x <= l && y >= r)
		return tree[now];

	int mid = l + (r - l) / 2;

	ll ans = 0;

	ans = max(ans, find(now * 2, l, mid, x, y) );

	ans = max(ans, find(now * 2 + 1, mid + 1, r, x, y) );

	return ans;

}
 
ll findt(int now, int l, int r, int x, int y)
{
	if(r < x || l > y)
		return -1;
	if(x <= l && y >= r)
		return tree[now];
 
	int mid = l + (r - l) / 2;
 
	ll ans = 0;
 
	ans = max(ans, find(now * 2, l, mid, x, y) );
 
	ans = max(ans, find(now * 2 + 1, mid + 1, r, x, y) );
 
	return ans;
 
}


int main()
{
	ios::sync_with_stdio(false);

	cin.tie(0);

	cout.tie(0);

	int T;

	cin>>T;
	
	for(int m = 1; m <= T; m++)
	{
		memset(arr, 0, sizeof(arr));

		memset(tree, 0, sizeof(arr));

		int len;

		cin>>len;

		for(int i = 1; i <= len; i++)
		{
			cin>>arr[i];
		}

		ll ans = 0;
		
		buildtree(1, 1, len);

		for(int i = 1; i <= len; i++)
		{
			ans = max(ans,  findt(1, 1, len, i + 1, len) - arr[i]);
		}
		
		cout<<"Case #"<<m<<": "<<ans<<endl;
	}
    

    return 0;
}