CODEWITHSUNDEEP
c++
Mathematical Lie
Mathematical Lie

Reputation: 143

Pass vector by reference, modify elements c++

In c++ I pass a vector of 'Node' objects by reference to a function—addUnique—which either increments the 'count' property of an element in the vector or appends to the vector.

const char inputString[] = "aaccgtgacac";

int main(int argc, const char * argv[]) {
    std::vector <Node> nodes;
    for (char input: inputString) {
        addUnique(nodes, input);
    }
    
    for (Node node: nodes) {
        node.display();
    }
}

void addUnique(std::vector<Node>& list, char check) {
    for (Node used: list) {
        if (used.baseChar == check) {
            used.count++;
            return;
        }
    }
    Node node(check, 1);
    list.push_back(node);
}

class Node {
public:
    char baseChar;
    Node* composition1;
    Node* composition2;
    unsigned int count;
    
    Node(char newChar, unsigned int newCount) {
        baseChar = newChar;
        count = newCount;
    }
    void display();
};

The main function then outputs the returned cont values with their corresponding charValues:

Upvotes: 0

Views: 902

Answers (1)

super
super

Reputation: 12928

Your loop where you increment the count, is iterating the Nodes by value:

for (Node used: list) { ... }

This makes a copy of each node, then you modify the copy and throw it away. Instead, make the loop use references:

for (Node& used: list) { ... }

Now you will modify the values in the vector, instead of the copy.

Upvotes: 1

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