计算24点是一种扑克牌益智游戏，随机抽出4张扑克牌，通过加(+)，减(-)，乘(*), 除(/)四种运算法则计算得到整数24，本问题中，扑克牌通过如下字符或者字符串表示，其中，小写joker表示小王，大写JOKER表示大王：
3 4 5 6 7 8 9 10 J Q K A 2 joker JOKER
本程序要求实现：输入4张牌，输出一个算式，算式的结果为24点。
详细说明：
输入4张牌为字符串形式，以一个空格隔开，首尾无空格；
如果输入的4张牌中包含大小王，则输出字符串“ERROR”，表示无法运算；
A A A A
NONE
#include<bits/stdc++.h>
using namespace std;
//根据k的不同进行计算
double ff(double a,double b,int k){
//cout<<"ff"<<endl;
if (k == 0){
return a+b;}
if (k == 1){
return a-b;}
if (k == 2){
return a*b;}
if (k == 3){
return a/b;}
}
//根据k的不同进行符号打印
string fff(int k){
if (k == 0){
return "+";}
if (k == 1){
return "-";}
if (k == 2){
return "*";}
if (k == 3){
return "/";}
}
//根据不同数字翻译牌的字符
string zz(int k){
if (k == 13){
return "K";}
if (k == 12){
return "Q";}
if (k == 11){
return "J";}
if (k == 1){
return "A";}
else{
return to_string(k);}
}
//计算=24的可能数字
vector<int> helper(int a,int b,int c,int d){
//cout<<"!!"<<endl;
for (int i=0;i<4;i++){
//cout<<"!!!"<<endl;
for (int j=0;j<4;j++){
for (int k=0;k<4;k++){
double tmp = ff(ff(ff(double(a),double(b),k),double(c),j),double(d),i);
//cout<<i<<" "<<j<<" "<<k<<" "<<tmp<<endl;
if (abs(tmp - 24)<0.0001)
return {k,j,i};
}}}
return {};
}
//回溯情况，这里可以优化重复情况，但是a了就算了
vector<vector<int>> pl(vector<int> &nums){
if (nums.size()==1){
return {{nums[0]}};}
vector<vector<int>> tmp ;
for (int i=0;i<nums.size();i++){
vector<int> tt;
for (int j=0;j<i;j++){
tt.push_back(nums[j]);
}
for (int j=i+1;j<nums.size();j++){
tt.push_back(nums[j]);
}
//cout<<"tt.size()"<<tt.size()<<endl;
auto t = pl(tt);
for (auto j: t){
j.insert(j.begin(),nums[i]);
tmp.push_back(j);
}
}
return tmp;
}
int main(){
vector<string> a(4,"");
for (int i=0;i<4;i++){
cin>>a[i];
}
vector<int> aa(4,0);
int ok = 1;
int ii = -1;
for (auto i:a){
ii++;
if (i == "J"){
aa[ii] = 11;
}
else if(i == "Q"){
aa[ii] = 12;
}
else if(i == "K"){
aa[ii] = 13;
}
else if(i == "A"){
aa[ii] = 1;
}
else if(i == "joker" || i == "JOKER"){
cout<<"ERROR";
ok = 0;
}
else{
aa[ii] = stod(i);
}
}
auto pailie = pl(aa);
int chenggong=0;
if (ok==1){
for (auto i:pailie){
auto ans= helper(i[0],i[1],i[2],i[3]);
if (ans.size()>0){
cout<<zz(i[0])+fff(ans[0])+zz(i[1])+fff(ans[1])+zz(i[2])+fff(ans[2])+zz(i[3])<<endl;
chenggong = 1;
break;
}
}
if (chenggong == 0){
cout<<"NONE"<<endl;
}
}
}
#include <iostream>
#include <vector>
#include <string>
#include <cmath>
using namespace std;
vector<string> result;
vector<string> poker;
vector<double> num;
bool dfs(int n)
{
if (n == 1)
{
/*cout << num[0] << " " << result[0] << endl;*/
if (fabs(num[0] - 24.0) < 1e-6)
{
return true;
}
return false;
}
double a, b;
string expa, expb;
for (int i = 0; i < n; ++i)
{
for (int j = i + 1; j < n; ++j)
{
a = num[i];
b = num[j];
num[j] = num[n - 1];
expa = result[i];
expb = result[j];
result[j] = result[n - 1];
num[i] = a + b; result[i] = /*'(' +*/ expa + '+' + expb /*+ ')'*/; if (dfs(n - 1)) return true;
num[i] = a - b; result[i] = /*'(' +*/ expa + '-' + expb /*+ ')'*/; if (dfs(n - 1)) return true;
num[i] = b - a; result[i] = /*'(' +*/ expb + '-' + expa /*+ ')'*/; if (dfs(n - 1)) return true;
num[i] = a * b; result[i] = /*'(' +*/ expa + '*' + expb /*+ ')'*/; if (dfs(n - 1)) return true;
//除法分母不为0
if (b != 0)
{
num[i] = a / b; result[i] = /*'(' +*/ expa + '/' + expb /*+ ')'*/; if (dfs(n - 1)) return true;
}
if (a != 0)
{
num[i] = b / a; result[i] = /*'(' +*/ expb + '/' + expa /*+ ')'*/; if (dfs(n - 1)) return true;
}
//回溯
num[i] = a;
num[j] = b;
result[i] = expa;
result[j] = expb;
}
}
return false;
}
int main()
{
string s;
for(int i = 0; i <4; ++i)
{
cin >> s;
result.push_back(s);
poker.push_back(s);
}
for (auto str : poker)
{
if (str.length() > 2)
{
cout << "ERROR" << endl;
return 0;
}
if (str.length() > 1)
{
num.push_back(10.0);
}
else if (str == "A")
{
num.push_back(1.0);
}
else if (str == "J")
{
num.push_back(11.0);
}
else if (str == "Q")
{
num.push_back(12.0);
}
else if (str == "K")
{
num.push_back(13.0);
}
else
{
num.push_back((str[0] -'0') * 1.0);
}
}
if (dfs(4))
{
cout << result[0] << endl;
}
else
{
cout << "NONE" << endl;
}
} 
#include <bits/stdc++.h>
using namespace std;
unordered_map<int, string> umap = {
{1, "A"}, {2, "2"}, {3, "3"}, {4, "4"}, {5, "5"}, {6, "6"}, {7, "7"},
{8, "8"}, {9, "9"}, {10, "10"}, {11, "J"}, {12, "Q"}, {13, "K"}};
void game24(vector<int>& num, string& item, int& total) {
if (num.empty() && total == 24)
return;
else if (num.empty())
return;
for (int i = 0; i < num.size(); ++i) {
int tmp = num[i];
swap(num[i], *num.rbegin());
num.pop_back();
total += tmp;
item = item + '+' + umap[tmp];
game24(num, item, total);
if (num.empty() && total == 24)
return;
item = item.substr(0, item.size() - (1 + umap[tmp].size()));
total -= tmp;
total -= tmp;
item = item + '-' + umap[tmp];
game24(num, item, total);
if (num.empty() && total == 24)
return;
item = item.substr(0, item.size() - (1 + umap[tmp].size()));
total += tmp;
total *= tmp;
item = item + '*' + umap[tmp];
game24(num, item, total);
if (num.empty() && total == 24)
return;
item = item.substr(0, item.size() - (1 + umap[tmp].size()));
total /= tmp;
if (total % tmp == 0) {
total /= tmp;
item = item + '/' + umap[tmp];
game24(num, item, total);
if (num.empty() && total == 24)
return;
item = item.substr(0, item.size() - (1 + umap[tmp].size()));
total *= tmp;
}
num.push_back(tmp);
swap(num[i], *num.rbegin());
}
return;
}
int main(){
vector<string> nums(4,"");
for(int i=0;i<4;++i){
cin>>nums[i];
}
vector<int> num;
for(int i=0; i<nums.size(); ++i){
if(nums[i]=="A"){
num.push_back(1);
}else if(nums[i]=="J"){
num.push_back(11);
}else if(nums[i]=="Q"){
num.push_back(12);
}else if(nums[i]=="K"){
num.push_back(13);
}else if(nums[i]=="joker"||nums[i]=="JOKER"){
cout << "ERROR" <<endl;
return 0;
}else{
num.push_back(stoi(nums[i].c_str()));
}
}
string item = "";
for (int i = 0; i < num.size(); ++i) {
int total = num[i];
swap(num[i], *num.rbegin());
num.pop_back();
item += umap[total];
game24(num, item, total);
if (num.empty() && total == 24) {
cout << item << endl;
return 0;
} else {
num.push_back(total);
swap(num[i], *num.rbegin());
item = "";
}
}
cout << "NONE" << endl;
return 0;
} 类似于全排列。#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;
bool visited[5]={0};
int num[5]={0};
int tempnum[5]={0};
char op[5]={0};
const string card[15]={"zero","A","2","3","4","5","6","7","8","9","10","J","Q","K"};
bool success=false;
void dfs(int level,double res)
{
if(success)
return;
if(level==4&&fabs(res-24)<1e-5)
{
success=true;
cout<<card[tempnum[0]];
for(int i=1;i<4;i++)
cout<<op[i]<<card[tempnum[i]];
cout<<endl;
return;
}
for(int i=0;i<4;i++)
{
if(!visited[i])
{
tempnum[level]=num[i];
visited[i]=true;
op[level]='+';
dfs(level+1,res+num[i]);
op[level]='-';
dfs(level+1,res-num[i]);
op[level]='*';
dfs(level+1,res*num[i]);
op[level]='/';
dfs(level+1,res/(double)num[i]);
tempnum[level]=0;
visited[i]=false;
}
}
}
int main()
{
string s[4];
for(int i=0;i<4;i++)
cin>>s[i];
for(int i=0;i<4;i++)
{
if(s[i]=="joker"||s[i]=="JOKER")
{
cout<<"ERROR"<<endl;
return 0;
}
else{
switch(s[i][0]){
case 'A':num[i]=1;break;
case 'J':num[i]=11;break;
case 'Q':num[i]=12;break;
case 'K':num[i]=13;break;
case '1':num[i]=10;break;
default:num[i]=s[i][0]-'0';break;
}
}
}
for(int i=0;i<4;i++)
{
tempnum[0]=num[i];
visited[i]=true;
dfs(1,num[i]);
//tempnum[0]=-num[i];
//dfs(1,-num[i]);
//样例没有负数，请不要取消注释。
visited[i]=false;
tempnum[0]=0;
}
if(!success)
cout<<"NONE"<<endl;
return 0;
}
简单的DFS。各位大佬的思路应该都是正确的，主要是输出算式的格式，并不是输出权值，而是输出原来的牌（A,J,Q,K）。题干里给出的1+2+3*4有一定误导性，让人以为是输出权值1而不是A。题也不需要考虑首项负数的情况，如-1/5+5*5,考虑了反而会出错吧。
#include <iostream>
#include <unordered_map>
#include <vector>
using namespace std;
static char opt[4] = {'+','-','*','/'};
static bool is_find = false;
int comp(vector<int>& nums, vector<char> op)
{
if(op.size() != 3) return 0;
int s = nums[0];
int j = 0;
for(int p = 0; p < 3 || j < 3; p++)
{
switch(op[j])
{
case '+' :
s += nums[p + 1];
break;
case '-' :
s -= nums[p + 1];
break;
case '*':
s *= nums[p + 1];
break;
case '/':
s /= nums[p + 1];
break;
}
j++;
}
return s;
}
void dfs(vector<int>& nums,int sum, vector<char>& op)
{
if(op.size() > 3 || is_find) return;
if(comp(nums, op) == sum)
{
cout << nums[0];
for(int k = 0;k < op.size();k++)
{
cout << op[k] << nums[k+1];
}
is_find = true;
return;
}
for(int idx = 0;idx < 3;idx++)
{
op.push_back(opt[idx]);
dfs(nums, sum, op);
op.pop_back();
}
}
int main()
{
unordered_map<string, int> m;
m["A"] = 1;
m["2"] = 2;
m["3"] = 3;
m["4"] = 4;
m["5"] = 5;
m["6"] = 6;
m["7"] = 7;
m["8"] = 8;
m["9"] = 9;
m["10"] = 10;
m["J"] = 11;
m["Q"] = 12;
m["K"] = 13;
vector<int> nums;
string a,b,c,d;
cin >> a >> b>> c >> d;
vector<string> str_num = {a,b,c,d};
for(const string& str : str_num)
{
if(m.find(str) == m.end())
{
cout << "ERROR" << endl;
return 0;
}
nums.push_back(m[str]);
}
vector<char>op;
dfs(nums,24, op);
if(!is_find)
cout << "NONE" << endl;
return 0;
} 
#include<iostream>
#include<vector>
#include<string>
#include<map>
using namespace std;
bool alluse(vector<int> &check){
for(auto num:check){
if(num==0)
return false;
}
return true;
}
bool dfs(vector<int> &num,vector<int> &check,vector<string> &res,int cal=0,bool ini=false){
if(alluse(check)){
if(cal==24)
return true;
else
return false;
}
for(int i=0;i<num.size();++i){
if(ini){
check[i]=1;
cal=num[i];
res.push_back(to_string(num[i]));
if(dfs(num,check,res,cal)){
return true;
}
res.pop_back();
check[i]=0;
}
else if(check[i]==0){
check[i]=1;
int temp;
temp=cal+num[i];
res.push_back("+");
res.push_back(to_string(num[i]));
if(dfs(num,check,res,temp)){
return true;
}
res.pop_back();
res.pop_back();
temp=cal-num[i];
res.push_back("-");
res.push_back(to_string(num[i]));
if(dfs(num,check,res,temp)){
return true;
}
res.pop_back();
res.pop_back();
temp=cal*num[i];
res.push_back("*");
res.push_back(to_string(num[i]));
if(dfs(num,check,res,temp)){
return true;
}
res.pop_back();
res.pop_back();
temp=cal/num[i];
res.push_back("/");
res.push_back(to_string(num[i]));
if(dfs(num,check,res,temp)){
return true;
}
res.pop_back();
res.pop_back();
check[i]=0;
}
}
return false;
}
int main(){
string s;
vector<string> poker;
vector<int> num;
map<string,string> mp;
while(cin>>s){
poker.push_back(s);
}
for(auto str:poker){
if(str.size()>2){
cout<<"ERROR"<<endl;
return 0;
}
else if(str.size()>1){
num.push_back(10);
}
else if(str=="A"){
num.push_back(1);
mp["1"]=str;
}
else if(str=="J"){
num.push_back(11);
mp["11"]=str;
}
else if(str=="Q"){
num.push_back(12);
mp["12"]=str;
}
else if(str=="K"){
num.push_back(13);
mp["13"]=str;
}
else{
num.push_back(str[0]-'0');
}
}
vector<int> check(num.size(),0);
vector<string> res;
if(!dfs(num,check,res,0,true)){
cout<<"NONE"<<endl;
return 0;
}
for(auto str:res){
string s=str;
if(mp.count(s)!=0){
s=mp[s];
}
cout<<s;
}
cout<<endl;
return 0;
} 
#include<iostream>
using namespace std;
string s[4];// 存储四张牌
char ope[]={'+','-','*','/'};
string sx[]={"A","2","3","4","5","6","7","8","9","10","J","Q","K"};
char arr[3];// 存储运算符每一次排列的结果
int arr_s[4];// 存储四张牌每一次排列的结果
bool FLAG=true;// 全局判断是否已计算得到24点
// 寻找字符随对应的整数
int search(string cache){
for(int i=0;i<13;i++){
if(sx[i]==cache){
return i+1;
}
}
}
// 对四张牌排列去重
bool isok(int w){ for(int i=0;i<w;i++){ if(arr_s[i]==arr_s[w]){ return false; } } return true;
}
// 对四张牌进行全排列
void dfs_s(int w){ if(w==4&&FLAG){ bool ui = true;
int sum = search(s[arr_s[0]]);
for(int i=0;i<3&&FLAG&&ui;i++){
if(arr[i]=='+'){
sum += search(s[arr_s[i+1]]);
}
else if(arr[i]=='-'){
sum -= search(s[arr_s[i+1]]);
}
else if(arr[i]=='*'){
sum *= search(s[arr_s[i+1]]);
}
else if(arr[i]=='/'){
if(sum%search(s[arr_s[i+1]])==0){
sum /= search(s[arr_s[i+1]]);
}
else{
ui = false;
}
}
}
if(sum==24&&ui&&FLAG){
FLAG=false;
}
return ; } for(int i=0;i<4&&FLAG;i++){ arr_s[w] = i; if(isok(w)){ dfs_s(w+1); } }
}
// 对运算符进行部分排列
void dfs(int w){
if(w==3&&FLAG){
dfs_s(0);
return ;
}
for(int i=0;i<4&&FLAG;i++){
arr[w]=ope[i];
dfs(w+1);
}
}
int main()
{
bool flag = true;
for(int i=0;i<4;i++){
string str;
cin >> str;
s[i] = str;
if(s[i]=="joker"||s[i]=="JOKER"){
flag = false;
}
}
if(flag){
dfs(0);
if(FLAG){
cout << "NONE";
}
else{
cout << s[arr_s[0]]+arr[0]+s[arr_s[1]]+arr[1]+s[arr_s[2]]+arr[2]+s[arr_s[3]];
}
}
else{
cout << "ERROR";
}
return 0;
} 
import java.util.*;
public class Main {
static boolean exist;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String str = in.nextLine();
String[] strs = str.trim().split(" ");
exist = false;
boolean flag = false;
int[] nums = new int[strs.length];
for (int i = 0; i < strs.length; i++) {
if ("joker".equals(strs[i])) {
flag = true;
break;
} else if ("JOKER".equals(strs[i])) {
flag = true;
break;
}
try {
int temp = Integer.parseInt(strs[i]);
nums[i] = temp;
} catch (NumberFormatException e) {
int temp = 0;
if ("J".equals(strs[i])) {
temp = 11;
} else if ("Q".equals(strs[i])) {
temp = 12;
} else if ("K".equals(strs[i])) {
temp = 13;
} else if ("A".equals(strs[i])) {
temp = 1;
}
nums[i] = temp;
}
}
if (flag) {
System.out.println("ERROR");
} else {
//4个数里选1个
for(int i = 0; i < nums.length; i++) {
if (!exist) {
int temp = nums[i];
nums[i] = -1;
new Main().dfs(nums,temp,1,String.valueOf(temp));
//一轮结束数字要回溯
nums[i] = temp;
} else {
break;
}
}
if (!exist) {
System.out.println("NONE");
}
}
}
public void dfs(int[] nums,double current,int stopIndexOf,String str) {
if (stopIndexOf == 4) {
if (!exist && Math.abs(current - 24) < 1e-6) {
System.out.println(str);
exist = true;
}
return;
}
int temp;
for (int i = 0; i < nums.length; i++) {
if (nums[i] == -1) {
continue;
}
if (!exist) {
temp = nums[i];
nums[i] = -1;
dfs(nums,current + temp,stopIndexOf + 1,str + "+" + temp);
dfs(nums,current - temp,stopIndexOf + 1,str + "-" + temp);
dfs(nums,current * temp,stopIndexOf + 1,str + "*" + temp);
dfs(nums,current / temp,stopIndexOf + 1,str + "/" + temp);
nums[i] = temp;
} {
return;
}
}
}
} 
#include <iostream>
#include <string>
#include <vector>
using namespace std;
vector<string> split(string str, string xx)
{
string::size_type pos = 0;
vector<string> result;
str += xx;
string::size_type size = str.size();
for (string::size_type i = 0; i < size; i++)
{
pos = str.find(xx, i);
if (pos < size)
{
result.push_back(str.substr(i, pos - i));
i = pos + xx.size() - 1;
}
}
return result;
}
vector<string> getOperators(vector<int> nums)
{
vector<string> result;
double tempResult = 0;
int tempOp = 0;
for (int a = 0; a < 4; a++)
for (int b = 0; b < 4; b++)
for (int c = 0; c < 4; c++)
{
tempResult = nums[0];
for (string::size_type i = 1; i < nums.size(); i++)
{
if (i == 1) tempOp = a;
if (i == 2) tempOp = b;
if (i == 3) tempOp = c;
switch (tempOp)
{
case 0: tempResult += nums[i]; result.push_back("+"); break;
case 1: tempResult -= nums[i]; result.push_back("-"); break;
case 2: tempResult *= nums[i]; result.push_back("*"); break;
case 3: tempResult /= nums[i]; result.push_back("/"); break;
}
}
if (tempResult == 24.00f)
{
return result;
}
result.clear();
}
return result;
}
int main()
{
string input;
getline(cin, input);
vector<string> inputSplit = split(input, string(" "));
vector<int> result;
for (auto nowStr : inputSplit)
{
if (nowStr.c_str()[0] >= '2' && nowStr.c_str()[0] <= '9')
result.push_back(nowStr.c_str()[0] - '0');
else if (nowStr.compare("10") == 0)
result.push_back(10);
else if (nowStr.compare("J") == 0)
result.push_back(11);
else if (nowStr.compare("Q") == 0)
result.push_back(12);
else if (nowStr.compare("K") == 0)
result.push_back(13);
else if (nowStr.compare("A") == 0)
result.push_back(1);
else if (nowStr.compare("JOKER") == 0 || nowStr.compare("joker") == 0)
{
cout << "ERROR";
return 0;
}
else
{
cout << "ERROR";
return 0;
}
}
auto test = getOperators(result);
if (!test.empty())
{
cout << inputSplit[0];
for (vector<int>::size_type i = 1; i < inputSplit.size(); i++)
{
cout << test[i - 1] << inputSplit[i];
}
}
else
{
cout << "NONE";
}
} 
扫描二维码，关注牛客网
下载牛客APP，随时随地刷题
扫一扫，把题目装进口袋
扫描二维码，进入QQ群
扫描二维码，关注牛客公众号
京公网安备
11010502036488号
