I need first subsequence with sum equal to k but instead i'm getting all subsequences in this code. How to solve this?

Question

I'm returning true after a copy still i'm getting all sequences.

def subset(nums,tot):
    res=[]
    def sub_seq(curr,i,s):
        if i==len(nums):
            if s==tot:
                res.append(curr.copy())
                return True# Even I'm returning true its bot working
            return False
                
        curr.append(nums[i])
        s+=nums[i]
        sub_seq(curr,i+1,s)
                
        s-=nums[i]
        curr.pop()
        sub_seq(curr,i+1,s)
    sub_seq([],0,0)
    return res
    
print(subset([1,2,1],2))

Answer 1

You're returning True, but you're not using it to stop further processing. To do so, have the other recursive calls to sub_seq immediately cease continued processing when the recursive call returns True:

def subset(nums,tot):
    res=[]
    def sub_seq(curr,i,s):
        if i==len(nums):
            if s==tot:
                res.append(curr.copy())
                return True
            return False

        curr.append(nums[i])
        s+=nums[i]
        if sub_seq(curr, i+1, s):   # Stop immediately if it returned True and propagate the True
            return True

        s-=nums[i]
        curr.pop()
        return sub_seq(curr,i+1,s)  # Propagate whatever the recursive call returned
    sub_seq([],0,0)
    return res

print(subset([1,2,1],2))

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