uva 1201 - Taxi Cab Scheme（二分图匹配）

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题目链接：uva 1201 - Taxi Cab Scheme

建图，X和Y集合均为N个点，如果接完第i个人之后来得及接j，那么从Xi建一条边道Yj。做最大匹配，如果选中Xi到Yj这条边，说明i和j用的是同一辆车，那么需要几辆车即为没有边连入的Y集合点数个数，即为N-最大匹配数。

#include <cstdio>#include <cstring>#include <cstdlib>#include <vector>#include <algorithm>using namespace std;const int maxn = 505;int N, L[maxn], K[maxn];vector<int> G[maxn];bool S[maxn], T[maxn];struct Point {int x, y;void read() { scanf("%d%d", &x, &y); }}A[maxn], B[maxn];int dis(Point a, Point b) {return abs(a.x-b.x) + abs(a.y-b.y);}bool judge (int a, int b) {int last = K[a] + dis(B[a], A[a]) + dis(A[b], B[a]);return last < K[b];}bool match(int u) {S[u] = true;for (int i = 0; i < G[u].size(); i++) {int j = G[u][i];if (!T[j]) {T[j] = true;if (!L[j] || match(L[j])) {L[j] = u;return true;}}}return false;}int KM () {int ret = 0;memset(L, 0, sizeof(L));for (int i = 1; i <= N; i++) {memset(S, false, sizeof(S));memset(T, false, sizeof(T));if (match(i)) ret++;}return ret;}int main () {int cas;scanf("%d", &cas);while (cas--) {scanf("%d", &N);int h, m;for (int i = 1; i <= N; i++) {G[i].clear();scanf("%d:%d", &h, &m);K[i] = h * 60 + m;A[i].read(), B[i].read();}for (int i = 1; i <= N; i++) {for (int j = 1; j <= N; j++) if (i != j && judge(i, j))G[i].push_back(j);}printf("%d\n", N - KM());}return 0;}

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