Recursive method
Accepted100 version: use array to store data, use hash to represent whether it has been used
#include <stdio.h>
#include <string.h>
int count=0;
int hash[100]={
0};
int arr[30]={
0};
int n=0;
void choose(int m,int total){
if(total==40){
count++;
return;
}
for(int x=m;x<n;x++){
if(hash[arr[x]]==0&&arr[x]+total<=40){
hash[arr[x]]=1;
choose(x+1,arr[x]+total);
hash[arr[x]]=0;
}
}
}
int main(){
while(scanf("%d",&n)!=EOF){
memset(hash,0,sizeof(hash));
memset(arr,0,sizeof(arr));
for(int i=0;i<n;i++){
scanf("%d",&arr[i]);
}
choose(0,0);
printf("%d\n",count);
count=0;
}
return 0;
}
Wrong Answer50 version: directly use hash==0 to indicate whether the data exists, and recurse by setting hash=1 to indicate that it has been occupied, and hash=0 to indicate that it exists but not yet occupied (but I don’t know why I only get 50 points, please comment The zone guy helped point out)
#include <stdio.h>
#include <string.h>
int count=0;
int hash[50]={
-1};
void choose(int s,int total){
if(total==40){
count++;
return;
}
for(int x=s;x<=40;x++){
if(hash[x]==0&&x+total<=40){
hash[x]=1;
choose(x+1,x+total);//注意不要直接给total加上，要不然还要减回来
hash[x]=0;
}
}
}
int main(){
int n=0;
while(scanf("%d",&n)!=EOF){
count=0;
memset(hash,-1,sizeof(hash));
for(int i=0;i<n;i++){
int m=0;
scanf("%d",&m);
hash[m]=0;
}
choose(1,0);
printf("%d\n",count);
}
return 0;
}