Submission #809007

#	Time	Username	Problem	Language	Result	Execution time	Memory
809007		jakobrs	Wombats (IOI13_wombats)	C++17	55 / 100	20072 ms	27124 KiB

wombats

#include <algorithm>
#include <numeric>
#include <queue>
#include <vector>

#ifndef EVAL
#include <iostream>
#endif

#include "wombats.h"

#define entire(a) std::begin((a)), std::end((a))

const int64_t INF = 2'000'000'000'000;

struct Matrix {
    int64_t a1 = 0, a2 = INF, b1 = INF, b2 = 0;

    Matrix operator*(const Matrix &rhs) const {
        return {
            .a1 = std::min(a1 + rhs.a1, b1 + rhs.a2),
            .a2 = std::min(b2 + rhs.a2, a2 + rhs.a1),
            .b1 = std::min(a1 + rhs.b1, b1 + rhs.b2),
            .b2 = std::min(b2 + rhs.b2, a2 + rhs.b1),
        };
    }
};

template <typename T>
struct SegmentTree {
    std::vector<T> values;
    int offset;

    SegmentTree() : values(), offset() {}
    explicit SegmentTree(int sz) : values(2 * sz), offset(sz) {}

    void update(int i, T value) {
        i += offset;

        values[i] = value;

        propagate(i);
    }

    void propagate(int i) {
        while (i /= 2) values[i] = values[2 * i] * values[2 * i + 1];
    }

    T query(int l, int r) {
        l += offset;
        r += offset;

        T left, right;
        while (l < r) {
            if (l & 1) left = left * values[l++];
            if (r & 1) right = values[--r] * right;

            l >>= 1;
            r >>= 1;
        }

        return left * right;
    }
};

std::vector<std::vector<int>> h, v;
int r, c;
SegmentTree<Matrix> st;
void init(int R, int C, int H[5000][200], int V[5000][200]) {
    h.reserve(R);
    v.reserve(R);
    for (int i = 0; i < R; i++) {
        h.emplace_back(entire(H[i]));
        v.emplace_back(entire(V[i]));
    }
    r = R;
    c = C;

    int o = 1;
    while (o < 2 * R) o *= 2;
    st = SegmentTree<Matrix>(o);

    for (int i = 0; i < R; i++) {
        st.update(2 * i, {
                             .a2 = H[i][0],
                             .b1 = H[i][0],
                         });
        if (i + 1 < R) {
            st.update(2 * i + 1, {
                                     .a1 = V[i][0],
                                     .b2 = V[i][1],
                                 });
        }
    }
}

void changeH(int P, int Q, int W) {
    h[P][Q] = W;
    st.update(2 * P, {
                         .a2 = h[P][0],
                         .b1 = h[P][0],
                     });
}

void changeV(int P, int Q, int W) {
    v[P][Q] = W;
    st.update(2 * P + 1, {
                             .a1 = v[P][0],
                             .b2 = v[P][1],
                         });
}

int escape(int V1, int V2) {
    if (c == 2) {
        auto res = st.query(0, 2 * r);

        if (V1 == 0 && V2 == 0)
            return res.a1;
        else if (V1 == 0 && V2 == 1)
            return res.b1;
        else if (V1 == 1 && V2 == 0)
            return res.a2;
        else if (V1 == 1 && V2 == 1)
            return res.b2;
    } else {
        std::vector<int> dist(c, 0);

        dist[V1] = 0;
        for (int i = V1 + 1; i < c; i++) {
            dist[i] = dist[i - 1] + h[0][i - 1];
        }
        for (int i = V1 - 1; i >= 0; i--) {
            dist[i] = dist[i + 1] + h[0][i];
        }

        std::priority_queue<std::pair<int, int>> pq;

        for (int i = 0; i + 1 < r; i++) {
            // phase 1: process vertical segments
            for (int j = 0; j < c; j++) {
                dist[j] += v[i][j];
            }

            // phase 2: process horizontal segments
            while (!pq.empty()) pq.pop();  // whyy is there no pq.clear();
            for (int j = 0; j < c; j++) {
                pq.push({-dist[j], j});
            }
            while (!pq.empty()) {
                auto [d, j] = pq.top();
                pq.pop();
                d = -d;

                if (d > dist[j]) continue;

                if (j > 0 && dist[j - 1] > d + h[i + 1][j - 1]) {
                    dist[j - 1] = d + h[i + 1][j - 1];
                    pq.push({-dist[j - 1], j - 1});
                }
                if (j + 1 < c && dist[j + 1] > d + h[i + 1][j]) {
                    dist[j + 1] = d + h[i + 1][j];
                    pq.push({-dist[j + 1], j + 1});
                }
            }
        }

        return dist[V2];
    }
}

Compilation message (stderr)

grader.c: In function 'int main()':
grader.c:15:6: warning: variable 'res' set but not used [-Wunused-but-set-variable]
   15 |  int res;
      |      ^~~
wombats.cpp: In function 'int escape(int, int)':
wombats.cpp:169:1: warning: control reaches end of non-void function [-Wreturn-type]
  169 | }
      | ^

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 18 / 18
• Subtask 5: 0 / 21
• Subtask 6: 0 / 24