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// 988. Smallest String Starting From Leaf
#include "leetcode.h"
/*
* given the 'root' of a binary tree where each node has a value in the range
* '[0, 25]' representing letters 'a' to 'z'. return the lexicographically
* smallest string that starts at a leaf of this tree and ends at the root. as a
* reminder, any shorter prefix of a string is lexicographically smaller. a leaf
* of a node is a node that has no children.
*/
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
};
struct TreeNode *createNode(int val) {
struct TreeNode *new_node =
(struct TreeNode *)malloc(sizeof(struct TreeNode));
new_node->val = val;
new_node->left = NULL;
new_node->right = NULL;
return new_node;
}
int depth(struct TreeNode *root) {
return !root ? 0 : fmax(depth(root->left), depth(root->right)) + 1;
}
void process(struct TreeNode *root, int *small, char *res, char *data,
int idx) {
if (!root)
return;
data[idx] = root->val + 'a';
idx++;
if (!root->left && !root->right) {
data[idx] = '\0';
if (root->val < *small) {
strcpy(res, data);
*small = root->val;
} else if (root->val == *small) {
int l_a = strlen(res) - 1, l_d = strlen(data) - 1;
while (l_a >= 0 && l_d >= 0) {
if (data[l_d] < res[l_a]) {
strcpy(res, data);
break;
}
if (data[l_d] > res[l_d])
break;
if (!l_d) {
strcpy(res, data);
break;
}
l_a--, l_d--;
}
}
}
process(root->left, small, res, data, idx);
process(root->right, small, res, data, idx);
}
char *smallestFromLeaf(struct TreeNode *root) {
int d = depth(root), small = 27;
char *data = calloc(d + 1, sizeof(char));
char *ans = calloc(d + 1, sizeof(char));
process(root, &small, ans, data, 0);
int n = strlen(ans);
for (int i = 0; i < n / 2; i++) {
char tmp = ans[i];
ans[i] = ans[n - i - 1];
ans[n - i - 1] = tmp;
}
return ans;
}
int main() {
struct TreeNode *root = createNode(0);
root->left = createNode(1);
root->right = createNode(2);
root->left->left = createNode(3);
root->left->right = createNode(4);
root->right->left = createNode(3);
root->right->right = createNode(4);
printf("%s\n", smallestFromLeaf(root));
}
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