codeforces B. Two Arrays And Swaps

题目

题意：

选择$a,b$a,b数据中的各$k$k个数字进行交换，最后要使得$a$a的总和最大。

思路：

我们将$a,b$a,b都排个序，然后在$k$k个数字中，如果出现$b_i>a_i$bi​>ai​的情况，那么就交换。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <vector>
#include <string>
#include <cmath>
#include <set>
#include <map>
#include <deque>
#include <stack>
#include <cctype>
using namespace std;
typedef long long ll;
typedef vector<int> veci;
typedef vector<ll> vecl;
typedef pair<int, int> pii;
template <class T>
inline void read(T &ret) {
    char c;
    int sgn;
    if (c = getchar(), c == EOF) return ;
    while (c != '-' && (c < '0' || c > '9')) c = getchar();
    sgn = (c == '-') ? -1:1;
    ret = (c == '-') ? 0:(c - '0');
    while (c = getchar(), c >= '0' && c <= '9') ret = ret * 10 + (c - '0');
    ret *= sgn;
    return ;
}
inline void out(int x) {
    if (x > 9) out(x / 10);
    putchar(x % 10 + '0');
}
bool cmp(int a, int b) {return a > b;}
int main() {
    int t;
    read(t);
    while (t--) {
        int n, k;
        read(n), read(k);
        int a[50] = {0}, b[50] = {0};
        for (int i = 0; i < n; i++) read(a[i]);
        for (int i = 0; i < n; i++) read(b[i]);
        sort(a, a + n);
        sort(b, b + n, cmp);
        for (int i = 0; i < k; i++) {
            if (a[i] < b[i]) swap(a[i], b[i]);
        }
        int ans = 0;
        for (int i = 0; i < n; i++) ans += a[i];
        out(ans);
        putchar('\n');
    }
    return 0;
}