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  • [线段树] [51nod] 1174 区间中最大的数

    裸线段树

    且只有查询

    基础

    #pragma GCC optimize(2)
    #include <iostream>
    #include <cmath>
    #include <iomanip>
    
    using namespace std;
    
    const int MAXN = 1e6 + 10;
    
    typedef long long ll;
    
    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;
    
    }
    
    int main()
    {
    	ios::sync_with_stdio(false);
    
    	cin.tie(0);
    
    	cout.tie(0);
    
        int N, T;
    
        cin>>N;
    
        for(int i = 1; i <= N; i++)
        	cin>>arr[i];
    
        buildtree(1, 1, N);
    	
    	//for(int i = 0; i < 10; i++)
    		//cout<<i<<' '<<tree[i]<<endl;
    		
        cin>>T;
    
        while(T--)
        {
        	int x, y;
    
        	cin>>x>>y;
    
        	cout<<find(1, 1, N, x + 1, y + 1)<<endl;
        }
    
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/zeolim/p/12270515.html
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