21-5-22校賽G 自行車調(diào)度

n個點，m條邊的無向帶正權圖（編號1到n)。每個點初始有a[i]（0<=a[i]<=1e5,1<=i<=n)輛自行車，自行車管理員可以花費一個邊權的代價移動一輛自行車從邊的一端到另一端。求自行車管理員所需的最小的代價使每個點自行車數(shù)量相等（無解輸出-1）。

調(diào)度問題，百分之九十都是網(wǎng)絡流，這個題是圖上的費用流
直接在原圖跑費用流就好了啊，我在干什么，還建了個完全二分圖。。

const int N = 510, inf = 1e9; int a[N], head[N], num, now[N], s, t, dis[N]; long long ans = 0; bool vis[N];struct edge {int nxt, to, val, pri; }; edge e[1000010];void addEdge(int x, int y, int z, int w) {e[++ num].nxt = head[x];head[x] = num;e[num].to = y;e[num].val = z;e[num].pri = w; }bool spfa() {for (int i = 0; i <= t; i ++)dis[i] = inf;dis[s] = 0;queue <int> q;q.push(s);while (!q.empty()){int x = q.front(); q.pop();for (int i = head[x]; i != -1; i = e[i].nxt){int to = e[i].to;if (dis[to] > dis[x] + e[i].pri)if (e[i].val > 0){dis[to] = dis[x] + e[i].pri;q.push(to);}}}if (dis[t] != inf) return true;return false; }int dfs(int x, int flow) {if (vis[x]) return 0;vis[x] = 1;if (x == t)return flow;for (int i = now[x]; i != -1; i = e[i].nxt){now[x] = i;if (dis[e[i].to] == dis[x] + e[i].pri && e[i].val > 0){int val = dfs(e[i].to, min(e[i].val, flow));if (val > 0){e[i].val -= val;e[i ^ 1].val += val;ans += (long long) val * e[i].pri;return val;} }}return 0; }int main() {int T = 1;T = read();while (T --){int n, m, sum = 0;num = -1;n = read(); m = read();memset (head, -1, sizeof (head));for (int i = 1; i <= n; i ++){a[i] = read();sum += a[i];}for (int i = 1; i <= m; i ++){int u, v, w;u = read(); v = read(); w = read();addEdge(u, v, inf, w);addEdge(v, u, 0, -w);addEdge(v, u, inf, w);addEdge(u, v, 0, -w);}if (sum % n != 0){printf ("-1\n");continue;}sum /= n;int tot = 0;for (int i = 1; i <= n; i ++){a[i] -= sum;if (a[i] > 0){addEdge(0, i, a[i], 0);addEdge(i, 0, 0, 0);tot += a[i];}if (a[i] < 0){addEdge(i, n + 1, -a[i], 0);addEdge(n + 1, i, 0, 0);}}s = 0; t = n + 1;ans = 0; int val;while (spfa()){for (int i = 0; i <= t; i ++){vis[i] = 0;now[i] = head[i];}while (val = dfs(s, inf)){tot -= val;}}if (tot > 0){printf ("-1\n");continue;}printf ("%lld\n", ans);}return 0; } 與50位技術專家面對面20年技術見證，附贈技術全景圖

總結(jié)

以上是生活随笔為你收集整理的21-5-22校赛G 自行车调度的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯，歡迎將生活随笔推薦給好友。