流淌的喷泉(Flowing Fountain) 题解

思路分析

按题目要求使用对应数据结构与算法模拟/递推求解，注意数据范围边界与时间复杂度。

参考代码

#include <iostream>
#include <vector>
#include <numeric>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, q;
    if (!(cin >> n >> q)) return 0;
    vector<long long> cap(n + 1), cur(n + 1, 0);
    for (int i = 1; i <= n; ++i) cin >> cap[i];
    vector<int> nxt(n + 2, n + 1), st;
    for (int i = 1; i <= n; ++i) {
        while (!st.empty() && cap[st.back()] < cap[i]) {
            nxt[st.back()] = i;
            st.pop_back();
        }
        st.push_back(i);
    }
    vector<int> p(n + 2);
    iota(p.begin(), p.end(), 0);
    auto find = [&](auto& self, int x) -> int {
        return p[x] == x ? x : p[x] = self(self, p[x]);
    };
    for (int i = 0; i < q; ++i) {
        char op;
        cin >> op;
        if (op == '+') {
            int l;
            long long x;
            cin >> l >> x;
            int u = find(find, l);
            while (u <= n && x > 0) {
                long long need = cap[u] - cur[u];
                if (x < need) {
                    cur[u] += x;
                    x = 0;
                } else {
                    cur[u] = cap[u];
                    x -= need;
                    p[u] = find(find, nxt[u]);
                    u = p[u];
                }
            }
        } else {
            int l;
            cin >> l;
            cout << cur[l] << "\n";
        }
    }
    return 0;
}