Leetcode problem of the day: integers to trie (concisely).

leetcode/3043.cpp

@@ -0,0 +1,90 @@
+#include <algorithm>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+using std::vector;
+
+struct node {
+    node* next[10] = {};
+};
+
+int count_digits(int i) {
+    int ans = 0;
+    while (i > 0) {
+        i /= 10;
+        ans++;
+    }
+    return ans;
+}
+
+static int p10s[] = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000};
+
+node arr2tree(vector<int> const& arr) {
+    node root;
+    for (const int a : arr) {
+        node* node_ptr = &root;
+        const int n = count_digits(a);
+        for (int i = 0; i < n; i++) {
+            const int d = (a / p10s[n - i - 1]) % 10;
+            if (!node_ptr->next[d]) node_ptr->next[d] = new node();
+            node_ptr = node_ptr->next[d];
+        }
+    }
+    return root;
+}
+
+int f(node root, int a) {
+    const int n = count_digits(a);
+    node* node_ptr = &root;
+    int ans = 0;
+    for (int i = 0; i < n; i++) {
+        const int d = (a / p10s[n - i - 1]) % 10;
+        if (!node_ptr->next[d]) return ans;
+        ans++;
+        node_ptr = node_ptr->next[d];
+    }
+    return ans;
+}
+
+void free(node* node_ptr) {
+    for (int i = 0; i < 10; i++) if (node_ptr->next[i]) free(node_ptr->next[i]);
+    delete node_ptr;
+}
+
+void free(node root) {
+    vector<node*> nodes;
+    for (int i = 0; i < 10; i++) if (root.next[i]) free(root.next[i]);
+}
+
+int longest_common_prefix(vector<int> const& arr1, vector<int> const& arr2) {
+    node root = arr2tree(arr1);
+    int ans = 0;
+    for (const int a : arr2) ans = std::max(ans, f(root, a));
+    free(root);
+    return ans;
+}
+
+TEST(longest_common_prefix, warming_up) {
+    const vector<int> arr1{1, 10, 100};
+    const vector<int> arr2{1000};
+    EXPECT_EQ(longest_common_prefix(arr1, arr2), 3); }
+
+TEST(longest_common_prefix, four) {
+    const vector<int> arr1{10987654, 123, 87654321, 654321};
+    const vector<int> arr2{109876, 1234567, 87654321, 654};
+    EXPECT_EQ(longest_common_prefix(arr1, arr2), 8); }
+
+TEST(longest_common_prefix, five) {
+    const vector<int> arr1{123987, 567890, 234567, 890123, 456789};
+    const vector<int> arr2{908123, 456123, 789012, 234567};
+    EXPECT_EQ(longest_common_prefix(arr1, arr2), 6); }
+
+TEST(longest_common_prefix, six) {
+    const vector<int> arr1{1248,364524,73264823,2937935};
+    const vector<int> arr2{73249,94895,656324,239583,1249};
+    EXPECT_EQ(longest_common_prefix(arr1, arr2), 3); }
+
+int main(int argc, char **argv) {
+    testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS(); }