【HDOJ】2333 Assemble

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二分+貪心策略。其中注釋處很重要。

 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 100510 #define INF  100000000011 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     else26         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 }