feat(leetcode-daily): april 13

public/code/algorithms/leetcode-daily/cgn.cpp

@@ -0,0 +1,19 @@
+class Solution {
+public:
+    static constexpr long long MOD = 1e9 + 7;
+    long long mpow(long long a, long long b, long long mod=MOD) {
+        long long ans = 1;
+        while (b > 0) {
+            if (b & 1) {
+                ans = (ans * a) % MOD;
+            }
+            a = (a * a) % MOD;
+            b >>= 1;
+        }
+        return ans;
+    }
+    int countGoodNumbers(long long n) {
+        long long even_slots = (n + 1) / 2, odd_slots = n / 2;
+        return (mpow(5, even_slots) * mpow(4, odd_slots)) % MOD;
+    }
+};