【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 }
