「洛谷 P1631」序列合并

给定两个长度为 $n$ 的序列 $a,b$ ，定义 $c_{i,j} = a_i+b_j$ ，输出 $c$ 的 $n\times n$ 个元素中前 $k$ 小

$n\le10^5$

---

核心代码

struct S {
    int i, j;
    bool operator<(const S &rhs) const { return a[i] + b[j] > a[rhs.i] + b[rhs.j]; }
};
std::priority_queue<S> q;
rep(i, 1, n) q.push({i, 1}); // c[i][1]
rep(cnt, 1, n) {
    // pop c[i][j], push c[i][j+1]
    int i = q.top().i, j = q.top().j;
    q.pop();
    io.write(a[i] + b[j], ' ');
    ++j;
    if (j <= n) q.push({i, j});
}

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("inline")
// #pragma GCC optimize("-fgcse")
// #pragma GCC optimize("-fgcse-lm")
// #pragma GCC optimize("-fipa-sra")
// #pragma GCC optimize("-ftree-pre")
// #pragma GCC optimize("-ftree-vrp")
// #pragma GCC optimize("-fpeephole2")
// #pragma GCC optimize("-ffast-math")
// #pragma GCC optimize("-fsched-spec")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC optimize("-falign-jumps")
// #pragma GCC optimize("-falign-loops")
// #pragma GCC optimize("-falign-labels")
// #pragma GCC optimize("-fdevirtualize")
// #pragma GCC optimize("-fcaller-saves")
// #pragma GCC optimize("-fcrossjumping")
// #pragma GCC optimize("-fthread-jumps")
// #pragma GCC optimize("-funroll-loops")
// #pragma GCC optimize("-fwhole-program")
// #pragma GCC optimize("-freorder-blocks")
// #pragma GCC optimize("-fschedule-insns")
// #pragma GCC optimize("inline-functions")
// #pragma GCC optimize("-ftree-tail-merge")
// #pragma GCC optimize("-fschedule-insns2")
// #pragma GCC optimize("-fstrict-aliasing")
// #pragma GCC optimize("-fstrict-overflow")
// #pragma GCC optimize("-falign-functions")
// #pragma GCC optimize("-fcse-skip-blocks")
// #pragma GCC optimize("-fcse-follow-jumps")
// #pragma GCC optimize("-fsched-interblock")
// #pragma GCC optimize("-fpartial-inlining")
// #pragma GCC optimize("no-stack-protector")
// #pragma GCC optimize("-freorder-functions")
// #pragma GCC optimize("-findirect-inlining")
// #pragma GCC optimize("-fhoist-adjacent-loads")
// #pragma GCC optimize("-frerun-cse-after-loop")
// #pragma GCC optimize("inline-small-functions")
// #pragma GCC optimize("-finline-small-functions")
// #pragma GCC optimize("-ftree-switch-conversion")
// #pragma GCC optimize("-foptimize-sibling-calls")
// #pragma GCC optimize("-fexpensive-optimizations")
// #pragma GCC optimize("-funsafe-loop-optimizations")
// #pragma GCC optimize("inline-functions-called-once")
// #pragma GCC optimize("-fdelete-null-pointer-checks")
#define rep(i, l, r) for (int i = (l); i <= (r); ++i)
#define per(i, l, r) for (int i = (l); i >= (r); --i)
using std::cerr;
using std::endl;
using std::make_pair;
using std::pair;
typedef pair<int, int> pii;
typedef long long ll;
typedef unsigned int ui;
typedef unsigned long long ull;

// #define DEBUG 1  //调试开关
struct IO {
#define MAXSIZE (1 << 20)
#define isdigit(x) (x >= '0' && x <= '9')
    char buf[MAXSIZE], *p1, *p2;
    char pbuf[MAXSIZE], *pp;
#if DEBUG
#else
    IO() : p1(buf), p2(buf), pp(pbuf) {}
    ~IO() { fwrite(pbuf, 1, pp - pbuf, stdout); }
#endif
    inline char gc() {
#if DEBUG  //调试，可显示字符
        return getchar();
#endif
        if (p1 == p2) p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin);
        return p1 == p2 ? -1 : *p1++;
    }
    inline bool blank(char ch) { return ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t'; }
    template <class T>
    inline void read(T &x) {
        register double tmp = 1;
        register bool sign = 0;
        x = 0;
        register char ch = gc();
        for (; !isdigit(ch); ch = gc())
            if (ch == '-') sign = 1;
        for (; isdigit(ch); ch = gc()) x = x * 10 + (ch - '0');
        if (ch == '.')
            for (ch = gc(); isdigit(ch); ch = gc()) tmp /= 10.0, x += tmp * (ch - '0');
        if (sign) x = -x;
    }
    inline void read(char *s) {
        register char ch = gc();
        for (; blank(ch); ch = gc())
            ;
        for (; !blank(ch); ch = gc()) *s++ = ch;
        *s = 0;
    }
    inline void read(char &c) {
        for (c = gc(); blank(c); c = gc())
            ;
    }
    inline void push(const char &c) {
#if DEBUG  //调试，可显示字符
        putchar(c);
#else
        if (pp - pbuf == MAXSIZE) fwrite(pbuf, 1, MAXSIZE, stdout), pp = pbuf;
        *pp++ = c;
#endif
    }
    template <class T>
    inline void write(T x) {
        if (x < 0) x = -x, push('-');  // 负数输出
        static T sta[35];
        T top = 0;
        do {
            sta[top++] = x % 10, x /= 10;
        } while (x);
        while (top) push(sta[--top] + '0');
    }
    inline void write(const char *s) {
        while (*s != '\0') push(*(s++));
    }
    template <class T>
    inline void write(T x, char lastChar) {
        write(x), push(lastChar);
    }
} io;

const int N = 100100;
int a[N], b[N];

int main() {
#ifdef LOCAL
    freopen("input", "r", stdin);
#endif
    int n;
    io.read(n);
    rep(i, 1, n) io.read(a[i]);
    rep(j, 1, n) io.read(b[j]);
    struct S {
        int i, j;
        bool operator<(const S &rhs) const { return a[i] + b[j] > a[rhs.i] + b[rhs.j]; }
    };
    std::priority_queue<S> q;
    rep(i, 1, n) q.push({i, 1});
    rep(cnt, 1, n) {
        int i = q.top().i, j = q.top().j;
        q.pop();
        io.write(a[i] + b[j], ' ');
        ++j;
        if (j <= n) q.push({i, j});
    }
    return 0;
}