HDU-1427-速算24点
HDU-1427-速算24点
http://acm.hdu.edu.cn/showproblem.php?pid=1427
4个数通过 +，—，*，/和加括号，计算得24,
枚举数字和运算符，DFS即可，注意题目要求计算过程中都不能出现小数，所以做除法时稍作处理
枚举数组可用algorithm里的next_permutation
The next_permutation() function attempts to transform the given range of elements [start,end) into the next lexicographically greater permutation of elements. If it succeeds, it returns true, otherwise, it returns false.
#include<iostream>#include<cstdio>#include<cstring>#include<cstdlib>#include<algorithm>using namespace std;int flag;int num[4];int cmp(const void *a,const void *b){return *(int *)a-*(int *)b;}void dfs(int sum,int cur,int m){if(flag)return;if(m==3){if(sum+cur==24||sum-cur==24||sum*cur==24)flag=1;if(cur!=0&&sum%cur==0&&sum/cur==24)flag=1;return;}dfs(sum+cur,num[m+1],m+1); //先计算前一部分dfs(sum-cur,num[m+1],m+1);dfs(sum*cur,num[m+1],m+1);if(cur!=0&&sum%cur==0)dfs(sum/cur,num[m+1],m+1);dfs(sum,cur+num[m+1],m+1); //先计算后一部分，相当于加括号dfs(sum,cur-num[m+1],m+1); dfs(sum,cur*num[m+1],m+1);if(num[m+1]!=0&&cur%num[m+1]==0)dfs(sum,cur/num[m+1],m+1);}int main(){int i;char str[5];while(scanf("%s",str)!=EOF){if(strlen(str)==2)num[0]=10;else{if(str[0]=='A')num[0]=1;else if(str[0]=='J')num[0]=11;else if(str[0]=='Q')num[0]=12;else if(str[0]=='K')num[0]=13;elsenum[0]=str[0]-'0';}for(i=1;i<=3;i++){scanf("%s",str);if(strlen(str)==2) num[i]=10; else{ if(str[0]=='A') num[i]=1; else if(str[0]=='J') num[i]=11; else if(str[0]=='Q') num[i]=12; else if(str[0]=='K') num[i]=13; else num[i]=str[0]-'0';}}qsort(num,4,sizeof(num[0]),cmp);flag=0;do{dfs(num[0],num[1],1);}while(next_permutation(num,num+4)&&!flag);if(flag)printf("Yes\n");elseprintf("No\n");}return 0;}