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// Sums all nodes of a binary tree.
#include <datatype99.h>
#include <stdio.h>
// clang-format off
datatype(
BinaryTree,
(Leaf, int),
(Node, BinaryTree *, int, BinaryTree *)
);
// clang-format on
int sum(const BinaryTree *tree) {
match(*tree) {
of(Leaf, x) return *x;
of(Node, lhs, x, rhs) return sum(*lhs) + *x + sum(*rhs);
}
// Invalid input (no such variant).
return -1;
}
#define TREE(tree) ((BinaryTree *)(BinaryTree[]){tree})
#define NODE(left, number, right) TREE(Node(left, number, right))
#define LEAF(number) TREE(Leaf(number))
int main(void) {
const BinaryTree *tree = NODE(NODE(LEAF(1), 2, NODE(LEAF(3), 4, LEAF(5))), 6, LEAF(7));
/*
* Output:
* 28
*/
printf("%d\n", sum(tree));
return 0;
}
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