Codeforces Technocup 2017 Elimination Round 1 Problem D

Posted on | In ,

T-shirts Distribution

Solution sketch

Let the source node be $0$, shirt nodes from small to large are $[1, 6]$ respectively, participant nodes are $[7, 7 + n)$, and sink node be $7 + n$.

AC Code

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
#include <bits/stdc++.h>
using namespace std;
struct Edge {
    int to, cap, rev;
    Edge(int a, int b, int c)
    {
        to = a;
        cap = b;
        rev = c;
    }
};
const int INF = 0x3f3f3f3f;
const int MAX_V = 1 + 1 + 6 + 100100;
vector<vector<Edge>> g(MAX_V);
int level[MAX_V];
int iter[MAX_V];
inline void add_edge(int u, int v, int cap)
{
    g[u].push_back((Edge) {
        v, cap, (int)g[v].size()
    });
    g[v].push_back((Edge) {
        u, 0, (int)g[u].size() - 1
    });
}
void bfs(int s)
{
    memset(level, -1, sizeof(level)); // 用fill
    queue<int> q;
    level[s] = 0;
    q.push(s);
    while (!q.empty()) {
        int v = q.front();
        q.pop();
        for (int i = 0; i < int(g[v].size()); i++) {
            const Edge &e = g[v][i];
            if (e.cap > 0 && level[e.to] < 0) {
                level[e.to] = level[v] + 1;
                q.push(e.to);
            }
        }
    }
}
int dfs(int v, int t, int f)
{
    if (v == t)
        return f;
    for (int &i = iter[v]; i < int(g[v].size()); i++) { // &很重要
        Edge &e = g[v][i];
        if (e.cap > 0 && level[v] < level[e.to]) {
            int d = dfs(e.to, t, min(f, e.cap));
            if (d > 0) {
                e.cap -= d;
                g[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}
int max_flow(int s, int t)   // dinic
{
    int flow = 0;
    for (;;) {
        bfs(s);
        if (level[t] < 0)
            return flow;
        memset(iter, 0, sizeof(iter));
        int f;
        while ((f = dfs(s, t, INF)) > 0) {
            flow += f;
        }
    }
}
typedef pair<int, int> ii;
const char* shirts[] = {"S", "M", "L", "XL", "XXL", "XXXL"};
int main()
{
	int quantity[6];
	for(int i = 0; i < 6; i++)
		scanf("%d", &quantity[i]);
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++) {
		char inp[100];
		scanf("%s", inp);
		char *tmp = strtok(inp, ", ");
		while(tmp != NULL) {
			for(int j = 0; j < 6; j++) {
				if(strcmp(tmp, shirts[j]) == 0) {
					// printf("%s\n", tmp);
					add_edge(j + 1, 7 + i, 1);
					break;
				}
			}
			tmp = strtok(NULL, ", ");
		}
		add_edge(7 + i, 7 + n, 1);
	}
	for(int i = 1; i <= 6; i++) {
		if(quantity[i - 1] > 0)
			add_edge(0, i, quantity[i - 1]);
	}
	if(max_flow(0, 7 + n) == n) {
		printf("YES\n");
		map<int, int> ans;
		for(int i = 1; i <= 6; i++) {
			for(auto j : g[i]) {
				if(j.cap == 0 && j.to > 6) {
					ans[j.to] = i;
				}
			}
		}
		for(auto i : ans) {
			printf("%s\n", shirts[i.second - 1]);
		}
	} else {
		printf("NO\n");
	}
    return 0;
}