CODEWITHSUNDEEP
c++
Hardik Singh Negi
Hardik Singh Negi

Reputation: 76

Value not usable in constant expression C++

The following code is in C++ I am encountering the error of value is not usable in a constant expression error

int sumNumbers(TreeNode* root) {

    stack<pair<TreeNode*, int>> st;
    st.push(make_pair(root, root->val));
    int sum = 0;

    while(!st.empty()){
        pair<TreeNode*, int> temp = st.top();
        st.pop();
        TreeNode* node = temp.first;
        int value = temp.second;

        if(node->left==NULL && node->right==NULL){
            sum += value;
        }

        if(node->left){
            st.push(pair< node->left, value*10 + node->left->val >);
        }

        if(node->right){
            st.push(pair< node->right, value*10 + node->right->val >);
        }
    }

    return sum;
}

The error is in the line:

if(node->left){
            st.push(pair< node->left, value*10 + node->left->val >);
        }

The error is:

Line 29: Char 37: error: the value of 'node' is not usable in a constant expression st.push(pair< node->left, value*10 + node->left->val >);

I am not able to figure out why this error is encountered here?

Upvotes: 1

Views: 1750

Answers (1)

Matthieu Brucher
Matthieu Brucher

Reputation: 22023

You want to use make_pair instead to create an object, setting the template types automatically:

st.push(make_pair(node->left, value*10 + node->left->val));

And same for the right side.

Upvotes: 6

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