hdu 4648 Magic Pen 6（贪心）

题目链接：hdu 4648 Magic Pen 6

解题思路

将边权拆成等价两份分别加到两个节点上，但是考虑边权可能是奇数，所以将所有权值翻倍，最后答案除2即可。

代码

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long ll;const int maxn = 1e5 + 5;int N, M;ll W[maxn];int main () {    while (scanf("%d%d", &N, &M) == 2) {        int u, v; ll k;        for (int i = 1; i <= N; i++) {            scanf("%lld", &k);            W[i] = 2 * k;        }        while (M--) {            scanf("%d%d%lld", &u, &v, &k);            W[u] += k; W[v] += k;        }        ll p = 0, q = 0;        sort(W + 1, W + N + 1);        for (int i = 1; i <= N; i += 2) {            p += W[i], q += W[i+1];        }        printf("%lld\n", (q-p)>>1);    }    return 0;}