1 条题解

  • 0
    @ 2026-10-27 0:36:27

    思路与算法

    使用Johnson双机调度:A_i<=B_i的作业按A_i升序放前,余下作业按B_i降序放后,再按A累计时间与B完成时间模拟最短工期并输出顺序。

    正确性说明

    相邻两作业i,j按i先j后不劣的充分交换条件为min(A_i,B_j)<=min(A_j,B_i)。Johnson前后分组及组内排序满足该次序条件,反复交换可把任意最优顺序变成此顺序而不增工期。最终模拟B完工=max(A累计,B上次完工)+B_i准确包含等待。

    复杂度

    O(n log n D)时间、O(nD)空间,D为输入时间及总工期的最大数位数;含两个作业组初始化、排序与模拟。

    易错点

    A和B必须保持同一作业编号;多种最优顺序均合法。代码支持未给位数上限的非负整数,不以一个sum(A)+sum(B)代替双机重叠模拟。

    参考代码(C++11)

    #include <bits/stdc++.h>
    using namespace std;
    struct cpp_int {
        string s;
        bool neg;
        cpp_int(long long v = 0) : s(to_string(v)), neg(v < 0) {
            if (neg)
                s.erase(s.begin());
        }
        void norm() {
            auto p = s.find_first_not_of('0');
            s = p == string::npos ? "0" : s.substr(p);
            if (s == "0")
                neg = false;
        }
        static int cmpabs(const cpp_int &a, const cpp_int &b) {
            if (a.s.size() != b.s.size())
                return a.s.size() < b.s.size() ? -1 : 1;
            return a.s == b.s ? 0 : a.s < b.s ? -1 : 1;
        }
        friend bool operator<(const cpp_int &a, const cpp_int &b) {
            if (a.neg != b.neg)
                return a.neg;
            int c = cmpabs(a, b);
            return a.neg ? c > 0 : c < 0;
        }
        friend bool operator==(const cpp_int &a, const cpp_int &b) {
            return a.neg == b.neg && a.s == b.s;
        }
        friend bool operator!=(const cpp_int &a, const cpp_int &b) {
            return !(a == b);
        }
        friend bool operator>(const cpp_int &a, const cpp_int &b) {
            return b < a;
        }
        friend bool operator<=(const cpp_int &a, const cpp_int &b) {
            return !(b < a);
        }
        friend bool operator>=(const cpp_int &a, const cpp_int &b) {
            return !(a < b);
        }
        cpp_int operator-() const {
            cpp_int r = *this;
            if (r.s != "0")
                r.neg = !r.neg;
            return r;
        }
        friend cpp_int operator+(const cpp_int &a, const cpp_int &b) {
            cpp_int r;
            r.s.clear();
            int carry = 0;
            if (a.neg == b.neg) {
                int i = (int)a.s.size() - 1, j = (int)b.s.size() - 1;
                while (i >= 0 || j >= 0 || carry) {
                    int v = carry + (i >= 0 ? a.s[i--] - '0' : 0) + (j >= 0 ? b.s[j--] - '0' : 0);
                    r.s += char('0' + v % 10);
                    carry = v / 10;
                }
                r.neg = a.neg;
            } else {
                const cpp_int *x = &a, *y = &b;
                if (cmpabs(a, b) < 0)
                    swap(x, y);
                int i = (int)x->s.size() - 1, j = (int)y->s.size() - 1;
                while (i >= 0) {
                    int v = x->s[i--] - '0' - carry - (j >= 0 ? y->s[j--] - '0' : 0);
                    carry = v < 0;
                    if (carry)
                        v += 10;
                    r.s += char('0' + v);
                }
                r.neg = x->neg;
            }
            reverse(r.s.begin(), r.s.end());
            r.norm();
            return r;
        }
        friend cpp_int operator-(const cpp_int &a, const cpp_int &b) {
            return a + (-b);
        }
        friend cpp_int operator*(const cpp_int &a, int b) {
            cpp_int r;
            r.s.clear();
            long long carry = 0;
            long long z = b;
            if (z < 0)
                z = -z;
            for (int i = (int)a.s.size() - 1; i >= 0; i--) {
                carry += (a.s[i] - '0') * z;
                r.s += char('0' + carry % 10);
                carry /= 10;
            }
            while (carry) {
                r.s += char('0' + carry % 10);
                carry /= 10;
            }
            reverse(r.s.begin(), r.s.end());
            r.neg = a.neg ^ (b < 0);
            r.norm();
            return r;
        }
        friend cpp_int operator/(const cpp_int &a, int b) {
            cpp_int r;
            r.s.clear();
            long long rem = 0, z = b;
            if (z < 0)
                z = -z;
            for (char c : a.s) {
                rem = rem * 10 + c - '0';
                r.s += char('0' + rem / z);
                rem %= z;
            }
            r.neg = a.neg ^ (b < 0);
            r.norm();
            return r;
        }
        cpp_int &operator+=(const cpp_int &b) {
            *this = *this + b;
            return *this;
        }
        cpp_int &operator-=(const cpp_int &b) {
            *this = *this - b;
            return *this;
        }
        cpp_int &operator*=(int b) {
            *this = *this * b;
            return *this;
        }
        friend istream &operator>>(istream &in, cpp_int &a) {
            string v;
            if (in >> v) {
                a.neg = v[0] == '-';
                if (v[0] == '-' || v[0] == '+')
                    v.erase(v.begin());
                a.s = v;
                a.norm();
            }
            return in;
        }
        friend ostream &operator<<(ostream &out, const cpp_int &a) {
            if (a.neg)
                out << '-';
            return out << a.s;
        }
    };
    
    struct DS {
        vector<int> p, s;
        DS(int n) : p(n), s(n, 1) {
            iota(p.begin(), p.end(), 0);
        }
        int find(int u) {
            while (p[u] != u) {
                p[u] = p[p[u]];
                u = p[u];
            }
            return u;
        }
        bool join(int a, int b) {
            a = find(a);
            b = find(b);
            if (a == b)
                return false;
            if (s[a] > s[b])
                swap(a, b);
            p[a] = b;
            s[b] += s[a];
            return true;
        }
    };
    
    int main() {
        int n;
        cin >> n;
        vector<cpp_int> a(n), b(n);
        for (auto &x : a)
            cin >> x;
        for (auto &x : b)
            cin >> x;
        vector<int> lo, hi;
        for (int i = 0; i < n; i++)
            (a[i] <= b[i] ? lo : hi).push_back(i);
        sort(lo.begin(), lo.end(), [&](int x, int y) {
            return a[x] != a[y] ? a[x] < a[y] : x < y;
        });
        sort(hi.begin(), hi.end(), [&](int x, int y) {
            return b[x] != b[y] ? b[x] > b[y] : x < y;
        });
        lo.insert(lo.end(), hi.begin(), hi.end());
        cpp_int A = 0, B = 0;
        for (int i : lo) {
            A += a[i];
            B = max(A, B) + b[i];
        }
        cout << B << "\n";
        for (int i : lo)
            cout << i + 1 << " ";
        cout << "\n";
    }
    
    • 1

    信息

    ID
    1952
    时间
    1000ms
    内存
    64MiB
    难度
    普及
    标签
    递交数
    0
    已通过
    0
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