luoguP4643 阿狸和桃子的挑战 思维

Posted 2021-01-30 reverymoon

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看下数据范围：

(n leq 14)，emmmm，状压(dp)的分

(n leq 10000, m leq 100000)，emmmm.....???，这是什么数据范围？

再观察一下所求

点十分好控制，边非常不好控制

能不能把边转化为点呢？

把边给均分给两边的点？

诶，好像可以了.....

然后就没了.....

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#include <cstdio>
#include <vector>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

#define ll long long
#define ri register int
#define rep(io, st, ed) for(ri io = st; io <= ed; io ++)
#define drep(io, ed, st) for(ri io = ed; io >= st; io --)
    
#define gc getchar
inline int read() {
    int p = 0, w = 1; char c = gc();
    while(c > '9' || c < '0') { if(c == '-') w = -1; c = gc(); }
    while(c >= '0' && c <= '9') p = p * 10 + c - '0', c = gc();
    return p * w;
}

int n, m;
ll val[200050];

int main() {
    n = read(); m = read();
    rep(i, 1, n) val[i] = 2 * read();
    rep(i, 1, m) {
        int u = read(), v = read(), w = read();
        val[u] += w; val[v] += w;
    }
    sort(val + 1, val + n + 1);
    ll ans = 0;
    drep(i, n, 1) 
    if(!((n - i) & 1)) ans += val[i];
    else ans -= val[i];
    printf("%lld
", ans / 2);
    return 0;
}