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  • hdu 1754 I Hate It(线段树水题)

    》》点击进入原题测试《《

    思路:线段树水题,可以手敲

    #include<string>
    #include<iostream>
    #include<algorithm>
    
    #define lson l,m,rt<<1
    #define rson m+1,r,rt<<1|1
    
    using namespace std;
    
    
    const int maxn = 2e5 + 5;
    
    int tree[maxn << 2];
    
    
    void build(int l, int r, int rt)
    {
        if (l == r){
            cin >> tree[rt];
            return;
        }
        int m = (l + r) >> 1;
        build(lson);
        build(rson);
        tree[rt] = max(tree[rt << 1], tree[rt << 1 | 1]);
    }
    void update(int x, int ans, int l, int r, int rt)
    {
        if (l == r){
            tree[rt] = ans;
            return;
        }
        int m = (l + r) >> 1;
        if (x <= m)update(x, ans, lson);
        else update(x, ans, rson);
        tree[rt] = max(tree[rt << 1] , tree[rt << 1 | 1]);
    }
    int query(int L, int R, int l, int r, int rt)
    {
        if (L <= l&&r <= R){
            return tree[rt];
        }
        int m = (l + r) >> 1, ans = 0;
        if (L <= m)ans = max(ans, query(L, R, lson));
        if (R > m)ans = max(ans, query(L, R, rson));
        return ans;
    }
    void Print(int l, int r, int rt)
    {
        if (l == r){
            cout << rt << " = " << tree[rt] << endl;
            return;
        }
        cout << rt << " = " << tree[rt] << endl;
        int m = (l + r) >> 1;
        if (l <= m)Print(lson);
        if (r > m)Print(rson);
    }
    int main()
    {
        std::ios::sync_with_stdio(false);
        
        int n, q; 
        while (cin >> n >> q){
            build(1, n, 1);
            string flag; int i, j;
            while (q--){
                cin >> flag >> i >> j;
                if (flag == "U"){
                    update(i, j, 1, n, 1);
                //    Print(1, n, 1);
                }
                else if (flag == "Q"){
                    cout << query(i, j, 1, n, 1) << endl;
                }
            }
            
        }
    
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/zengguoqiang/p/9382487.html
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