The Accomodation of Students 二分图判定+匹配

模板题，复习一下模板

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int maxn = 205;int n, m, tot, head[maxn], vis[maxn], match[maxn];struct Edge { int to, next; } edges[maxn*maxn];void init() { tot = 0; memset(head, -1, sizeof(head)); }void addedge(int u, int v) {    edges[++tot].to = v; edges[tot].next = head[u]; head[u] = tot;}bool dfs(int u) {    for (int i = head[u]; ~i; i = edges[i].next) {        int v = edges[i].to;        if (vis[v]) {            if (vis[v] == -vis[u]) continue;            else return false;        }        else {            vis[v] = -vis[u];            if (!dfs(v)) return false;        }    }    return true;}bool solve(int u) {    vis[u] = 1;    for (int i = head[u]; ~i; i = edges[i].next) {        int v = edges[i].to, w = match[v];        if (w < 0 || !vis[w] && solve(w)) {            match[u] = v;            match[v] = u;            return true;        }    }    return false;}int maxflow() {    int ans = 0;    memset(match, -1, sizeof(match));    for (int i = 1; i <= n; i++) {        if (match[i] < 0) {            memset(vis, 0, sizeof(vis));            if (solve(i)) ans++;        }    }    return ans;}int main() {    int u, v;    while (~scanf("%d %d", &n, &m)) {        init();        for (int i = 1; i <= m; i++) {            scanf("%d %d", &u, &v);            addedge(u, v); addedge(v, u);        }        memset(vis, 0, sizeof(vis));        bool ok = true;        for (int i = 1; i <= n; i++) {            if (vis[i]) continue;            vis[i] = 1;            if (!dfs(i)) { ok = false; break; }        }        if (!ok) printf("No\n");        else printf("%d\n", maxflow());    }}