(Hdu step 4.2.7) Kill the Monster (there are n skills to find the minimum number of uses of the skill to kill monsters. When using a certain skill, if the monster's energy value is hp<=m, the damage is twice times the original value.

Topic:

Kill the Monster

Time limit:2000/1000 MS (java/others) Memory limit:32768/32768 K (java/others)

Total submission (s): 133 Accepted Submission (s): 97

Problem Descriptionthere is a mountain near Yifenfei ' s hometown. On the mountain lived a big monster. As a hero in hometown, Yifenfei wants to kill it. Now we know Yifenfei has n spells, and the monster has M hp, when HP <= 0 meaning monster is killed. Yifenfei ' s spells has different effect if used in different time. Now all you have spells ' s effects, expressed (A, M). A show the spell can cost A HP-monster in the common time. M show that is when the monster's HP <= M, using this spell can get double effect.

Inputthe input contains multiple test cases. Each test case include, first and integers n, m (2<n<10, 1<m<10^7), express how many spells Yifenfei have. Next n line, each line express one spell. (Ai, Mi). (0<ai,mi<=m).

Outputfor each test case output one integer, how many spells Yifenfei should with at least. If Yifenfei can not kill the monster output-1.

Sample Input 3 10010 2045 895 403 10010 2045 905 403 10010 2045 845 40

Sample Output 32-1

Authoryifenfei

The age of Source struggle

Recommendyifenfei

Topic Analysis:

Deep Search. Simple question. In fact, this problem basically no difficulty. Just read the subject.

The code is as follows:

/* * h.cpp * * Created on:2015 February 26 * author:administrator * * #include <iostream> #include <cstdio>usin G namespace Std;const int maxn = 11;struct node{//skill structure int spell;//damage value int m;//If this big trick is released, the monster's HP drizzle is the value, then the damage is spell*2 }node[maxn];bool visited[maxn];//is used to mark whether a skill has used an int ans;//kill a monster the minimum number of skills required int n;//Total skill number int hp;//Monster's energy value/** * Deep search. * k: Indicates the current number of skills * HP: The current Monster Energy value */void DFS (int k,int hp) {/** * Cross judgment */if (K >= 11) {//If all the skills have been put out of return;//Return.} /** * Determine if the */if is successful (HP <= 0) {//If the monster's energy value has been <=0if (ans > k) {//If the minimum number of skills currently saved < Current minimum skill number ans = k;//update the minimum number of skills in the bag village}return ;//Return}int i;for (i = 1; I <= n; ++i) {//Traverse all skills if (visited[i] = false) {//If the skill has not been used visited[i] = true;//mark the skill as already using if (h P <= Node[i]. M) {//If the monster's energy value <=mdfs (k+1,hp-node[i].spell*2);//Then the damage value is spell*2. Continue using the next skill}else{//otherwise DFS (K+1,hp-node[i]. spell);//This time caused the Shanghai city spell}visited[i] = false;//rollback. Mark the skill as not being accessed}}}int main () {while (scanf ("%d%d", &n,&hp)! = EOF) {int i;for (i = 1; I <= n; ++i) {scanf ("%d%d", &AMp;node[i].spell,&node[i]. M);} memset (visited,false,sizeof (visited)); ans = 11;//initialization skill minimum number of uses DFS (0,HP); if (ans = = 11) {//If ANS has not been updated printf (" -1\n") ;//Then prove that the monster was not killed}else{//otherwise, it proves that the monster was killed by printf ("%d\n", ans);//output using the minimum number of skills}}return 0;}

(Hdu step 4.2.7) Kill the Monster (there are n skills to find the minimum number of uses of the skill to kill monsters. When using a certain skill, if the monster's energy value is hp<=m, the damage is twice times the original value.