UVALive - 2531 The K-League(最大流＋枚舉)

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題目大意：有n支隊伍進行比賽，每支隊伍需要打的比賽次數相同，每場比賽恰好有一支隊伍勝，一支隊伍敗，給出每支隊伍目前勝的場數和敗的場數，以及每兩支隊伍還剩下的比賽場數，確定所有可能得冠軍的隊伍

解題思路：枚舉每支隊伍，然後讓該隊伍在接下來的所有比賽中都獲勝。
建圖的話，就比較簡單了，源點連向每場比賽，容量為比賽次數
每場比賽連向比賽隊伍，容量為比賽次數
接著每支隊伍連向匯點，容量為枚舉隊伍的總勝場－該隊伍的勝場

如果滿流，表示該隊伍可以得到冠軍

#include <cstdio>#include <cstring>#include <algorithm>#include <queue>using namespace std;#define M 1000010#define N 10010#define INF 0x3f3f3f3fstruct Edge{    int u, v, cap, flow, next;}E[M];struct Dinic{    int head[N], d[N];    int tot, sink, source;    void init() {        memset(head, -1, sizeof(head));        tot = 0;    }    inline void AddEdge(int u, int v, int cap) {        E[tot].u = u; E[tot].v = v; E[tot].cap = cap; E[tot].flow = 0; E[tot].next = head[u]; head[u] = tot++;        u = u ^ v; v = u ^ v; u = u ^ v;        E[tot].u = u; E[tot].v = v; E[tot].cap = 0; E[tot].flow = 0; E[tot].next = head[u]; head[u] = tot++;    }    inline bool bfs(int s) {        int u, v;        memset(d, 0, sizeof(d));        queue<int> Q;        Q.push(s);        d[s] = 1;        while (!Q.empty()) {            u = Q.front(); Q.pop();            if (u == sink) return true;            for (int i = head[u]; ~i; i = E[i].next) {                v = E[i].v;                if (!d[v] && E[i].cap - E[i].flow > 0) {                    d[v] = d[u] + 1;                    Q.push(v);                }            }        }        return false;    }    int dfs(int x, int a) {        if (x == sink || a == 0)            return a;        int f, flow = 0;        for (int i = head[x]; ~i; i = E[i].next) {            int v = E[i].v;            if (d[v] == d[x] + 1 && E[i].cap - E[i].flow > 0) {                f = dfs(v, min(a, E[i].cap - E[i].flow));                E[i].flow += f;                E[i^1].flow -= f;                flow += f;                a -= f;                if (!a) break;            }        }        if (flow == 0) d[x] = 0;        return flow;    }    int Maxflow(int source, int sink) {        int flow = 0;        this->sink = sink;        while (bfs(source)) flow += dfs(source, INF);        return flow;    }};Dinic dinic;#define maxn 30int n;int win[maxn], fight[maxn][maxn], all, Max;void init() {    scanf("%d", &n);    all = 0;    Max = -INF;    int t;    for (int i = 1; i <= n; i++) {        scanf("%d%d", &win[i], &t);        Max = max(Max, win[i]);        if (i == 1)            all += win[i] + t;    }    for (int i = 1; i <= n; i++)         for (int j = 1; j <= n; j++) {            scanf("%d", &fight[i][j]);            if (i == 1)                all += fight[i][j];        }}void solve() {    bool flag = false;    int total, source = 0, sink =  N - 1, cnt;    for (int i = 1; i <= n; i++) {        total = win[i];        for (int j = 1; j <= n; j++)            total += fight[i][j];        if (total < Max)            continue;        cnt = n + 1;        dinic.init();        int Sum = 0;        for (int j = 1; j <= n; j++) {            if (j != i) dinic.AddEdge(j, sink, total - win[j]);            for (int k = j + 1; k <= n; k++) {                if (j == i || k == i)                     continue;                dinic.AddEdge(source, cnt, fight[j][k]);                Sum += fight[j][k];                dinic.AddEdge(cnt, j, fight[j][k]);                dinic.AddEdge(cnt++, k, fight[j][k]);            }        }        int MaxFlow = dinic.Maxflow(source, sink);        if (MaxFlow == Sum) {            if (flag)                printf(" ");            flag = true;            printf("%d", i);        }    }    printf("\n");}int main() {    int test;    scanf("%d", &test);    while (test--) {        init();        solve();    }    return 0;}

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UVALive - 2531 The K-League(最大流＋枚舉)