题目链接
我们可以把图行列拆开,同时对于行/列拆成很多个联通块,然后考虑每个点所在的行联通块/列联通块的贡献。
可以这样建边
从S向每个行联通块连联通块大小条边,每条边的容量为1,费用为\(i\)(i表示这是第几条边)。
从每个点所在的行联通块向列联通块连边,容量为1,费用为0
从每个列联通块向T连联通块大小条边,每条边的容量为1,费用为\(i\)(i表示这是第几条边)。
这样跑最小费用最大流,每增光一次的费用就是答案。预处理后O(1)回答即可
#include<bits/stdc++.h> #define Pair pair<int, int> #define MP(x, y) make_pair(x, y) #define fi first #define se second //#define int long long #define LL long long #define ull unsigned long long #define Fin(x) {freopen(#x".in","r",stdin);} #define Fout(x) {freopen(#x".out","w",stdout);} using namespace std; const int MAXN = 5001, mod = 1e9 + 7, INF = 1e9 + 10; const double eps = 1e-9; template <typename A, typename B> inline bool chmin(A &a, B b){if(a > b) {a = b; return 1;} return 0;} template <typename A, typename B> inline bool chmax(A &a, B b){if(a < b) {a = b; return 1;} return 0;} template <typename A, typename B> inline LL add(A x, B y) {if(x + y < 0) return x + y + mod; return x + y >= mod ? x + y - mod : x + y;} template <typename A, typename B> inline void add2(A &x, B y) {if(x + y < 0) x = x + y + mod; else x = (x + y >= mod ? x + y - mod : x + y);} template <typename A, typename B> inline LL mul(A x, B y) {return 1ll * x * y % mod;} template <typename A, typename B> inline void mul2(A &x, B y) {x = (1ll * x * y % mod + mod) % mod;} template <typename A> inline void debug(A a){cout << a << '\n';} template <typename A> inline LL sqr(A x){return 1ll * x * x;} template <typename A, typename B> inline LL fp(A a, B p, int md = mod) {int b = 1;while(p) {if(p & 1) b = mul(b, a);a = mul(a, a); p >>= 1;}return b;} template <typename A> A inv(A x) {return fp(x, mod - 2);} inline int read() { char c = getchar(); int x = 0, f = 1; while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();} while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar(); return x * f; } int N, S, T , TT; char s[51][51]; int id[51][51][2], c1 = 1, c2 = 1, ans[MAXN * MAXN], tot1[20 * MAXN], tot2[20 * MAXN ], num1, num2; struct Edge { int u, v, w, f, nxt; }E[2 * MAXN * MAXN]; int head[MAXN * 20 + 1], num; void add_edge(int x, int y, int w, int f) { E[num] = (Edge){x, y, w, f, head[x]}; head[x] = num++; } void AddEdge(int x, int y, int w, int f) { //printf("%d %d %d %d\n", x, y, w, f); add_edge(x, y, w, f); add_edge(y, x, -w, 0); } int dis[MAXN * 10], vis[MAXN * 10], pre[MAXN * 10]; int SPFA() { memset(dis, 0x3f, sizeof(dis)); memset(vis, 0, sizeof(vis)); queue<int> q; q.push(S); dis[S] = 0; while(!q.empty()) { int p = q.front(); q.pop(); vis[p] = 0; for(int i = head[p]; ~i; i = E[i].nxt) { int to = E[i].v, w = E[i].w; if(dis[to] > dis[p] + w && E[i].f) { dis[to] = dis[p] + w; pre[to] = i; if(!vis[to]) vis[to] = 1, q.push(to); } } } return dis[TT]; } int MCMF() { int val = SPFA(), dec = INF; for(int k = TT; k != S; k = E[pre[k]].u) chmin(dec, E[pre[k]].f); for(int k = TT; k != S; k = E[pre[k]].u) E[pre[k]].f -= dec, E[pre[k] ^ 1].f += dec; return dec * val; } signed main() { //freopen("a.in", "r", stdin); memset(head, -1, sizeof(head)); N = read(); S = 0; T = N * N * 10, TT = T + 1; c2 = N * N * 3 + 1; for(int i = 1; i <= N; i++) scanf("%s", s[i] + 1); for(int i = 1; i <= N; i++) { for(int j = 1; j <= N; j++) { if(s[i][j] == '#') tot1[c1] = num1, num1 = 0, c1++; else id[i][j][0] = c1, num1++; if(s[j][i] == '#') tot2[c2] = num2, num2 = 0, c2++; else id[j][i][1] = c2, num2++; } if(num1) tot1[c1++] = num1, num1 = 0; if(num2) tot2[c2++] = num2, num2 = 0; } for(int i = 1; i <= N; i++) for(int j = 1; j <= N; j++) if(id[i][j][0] && id[i][j][1]) AddEdge(id[i][j][0], id[i][j][1], 0, 1); for(int i = 1; i <= c1; i++) for(int j = 0; j < tot1[i]; j++) AddEdge(S, i, j, 1); for(int i = N * N * 3 + 1; i <= c2; i++) for(int j = 0; j < tot2[i]; j++) AddEdge(i, T, j, 1); for(int i = 1; i <= 2 * N * N; i++) AddEdge(T, TT, 0, 1); for(int i = 1; i <= N * N; i++) ans[i] = ans[i - 1] + MCMF(); int Q = read(); while(Q--) cout << ans[read()] << '\n'; return 0; }