【HDOJ】2333 Assemble

二分+贪心策略。其中注释处很重要。

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cstdlib>
 5 #include <algorithm>
 6 using namespace std;
 7
 8 #define MAXL 25
 9 #define MAXN 1005
10 #define INF  1000000000
11
12 typedef struct {
13     char name[MAXL];
14     int p, q;
15 } comp_st;
16
17 comp_st comps[MAXN];
18 int t, n, b;
19 int ns[MAXN], nn;
20
21 bool comp(comp_st a, comp_st b) {
22     int tmp = strcmp(a.name, b.name);
23     if (tmp == 0)
24         return a.q > b.q;
25     else
26         return tmp < 0;
27 }
28
29 bool chk(int x) {
30     int i, j;
31     int sum = 0, min;
32
33     for (i=0; i<nn; ++i) {
34         min = INF;
35         for (j=ns[i]; j<ns[i+1]; ++j) {
36             if (comps[j].q>=x && min>comps[j].p)
37                 min = comps[j].p;
38         }
39         /* pay attention to here.*/
40         if (min == INF)
41             return false;
42         sum += min;
43     }
44     return sum<=b;
45 }
46
47 int main() {
48     int i, min, max, mid, v;
49     char str[MAXL];
50
51     scanf("%d", &t);
52
53     while (t--) {
54         scanf("%d %d", &n, &b);
55         min = INF;
56         max = 0;
57         for (i=0; i<n; ++i) {
58             scanf("%s %s %d %d", comps[i].name, str, &comps[i].p, &comps[i].q);
59             if (comps[i].q < min) min = comps[i].q;
60             if (comps[i].q > max) max = comps[i].q;
61         }
62         sort(comps, comps+n, comp);
63         ns[0] = 0;
64         for (nn=0,i=1; i<n; ++i) {
65             if (strcmp(comps[i-1].name, comps[i].name) != 0)
66                 ns[++nn] = i;
67         }
68         ns[++nn] = n;
69         v = 0;
70         while (min <= max) {
71             mid = (min+max)/2;
72             if ( chk(mid) ) {
73                 v = mid;
74                 min = mid+1;
75             } else {
76                 max = mid-1;
77             }
78         }
79         printf("%d\n", v);
80     }
81
82     return 0;
83 }

【HDOJ】2333 Assemble