HDU3697 Selecting courses
原题传送:http://acm.hdu.edu.cn/showproblem.php?pid=3697
贪心算法。起始点可能是0,1,2,3,4,枚举这5个起始点,后面的点选择可选策略是:选择符合该时刻且结束时间最早的。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include <stdio.h> 2 #include <string.h> 3 #define N 305 4 struct course 5 { 6 int s, t; 7 }e[N]; 8 9 int n; 10 bool vis[N]; 11 12 void work() 13 { 14 int ans, i, j, k, x, max; 15 max = 0; 16 for(i = 0; i < 5; i ++) 17 { 18 memset(vis, false, sizeof vis); 19 ans = 0; 20 for(j = i; j <= 1000; j += 5) 21 { 22 x = -1; 23 for(k = 0; k < n; k ++) 24 { 25 if(!vis[k] && e[k].s <= j && e[k].t > j) 26 if(x == -1 || e[k].t < e[x].t) 27 x = k; 28 } 29 if(x != -1) 30 ans ++, vis[x] = true; 31 } 32 if(ans > max) 33 max = ans; 34 } 35 printf("%d\n", max); 36 } 37 38 void read() 39 { 40 for(int i = 0; i < n; i ++) 41 scanf("%d%d", &e[i].s, &e[i].t); 42 } 43 44 int main() 45 { 46 while(scanf("%d", &n), n) 47 { 48 read(); 49 work(); 50 } 51 return 0; 52 }