PrintBinaryTree.java

/*
2 Given a binary tree, print out all of its root-to-leaf
3 paths, one per line. Uses a recursive helper to do the work.
4  */
void printPaths(struct node* node) {
    int path[1000];
    printPathsRecur(node, path, 0);
}

/*
Recursive helper function -- given a node, and an array containing
the path from the root node up to but not including this node,
print out all the root-leaf paths.
*/
void printPathsRecur(struct node* node, int path[], int pathLen) {
    if (node==NULL) 
        return;
    // append this node to the path array
    path[pathLen] = node->data;
    pathLen++;
    // it's a leaf, so print the path that led to here
    if (node->left==NULL && node->right==NULL) {
        printArray(path, pathLen);
    }
    else {
        // otherwise try both subtrees
        printPathsRecur(node->left, path, pathLen);
        printPathsRecur(node->right, path, pathLen);
    }
}

/*
Utility that prints out an array on a line.
*/
void printArray(int ints[], int len) {
    int i;
    for (i=0; i<len; i++) {
        printf("%d ", ints[i]);
    }
    printf("\n");
}