diff --git a/36. Valid Sudoku.cpp b/36. Valid Sudoku.cpp
new file mode 100644
index 0000000..b22cfbb
--- /dev/null
+++ b/36. Valid Sudoku.cpp	
@@ -0,0 +1,28 @@
+class Solution {
+public:
+    bool isValidSudoku(vector<vector<char>>& board) {
+        bitset<9> Col[9];
+        bitset<9> Row[9];
+        bitset<9> Block[9];
+
+        for(int i = 0; i < 9; i++){
+            for(int j = 0; j < 9; j++){
+                char c = board[i][j];
+                if (c == '.') continue;
+                int x = (c - '0') % 9;
+
+                if (Row[i][x]) return 0;
+                Row[i][x] = 1;
+
+                if (Col[j][x]) return 0;
+                Col[j][x] = 1;
+                
+                int bidx = (i / 3) * 3 + j / 3;
+                
+                if (Block[bidx][x]) return 0;
+                Block[bidx][x] = 1;
+            }
+        }
+        return 1;
+    }
+};
\ No newline at end of file
diff --git a/Number of People Aware of a Secret.cpp b/Number of People Aware of a Secret.cpp
new file mode 100644
index 0000000..6c9a52d
--- /dev/null
+++ b/Number of People Aware of a Secret.cpp	
@@ -0,0 +1,19 @@
+class Solution {
+public:
+    int peopleAwareOfSecret(int n, int delay, int forget) {
+        vector<long long> dp(n + 1, 0);
+        dp[1] = 1;
+        long long share = 0, MOD = 1000000007;
+        for (int t = 2; t <= n; t++) {
+            if (t - delay > 0)
+                share = (share + dp[t - delay] + MOD) % MOD;
+            if (t - forget > 0)
+                share = (share - dp[t - forget] + MOD) % MOD;
+            dp[t] = share;
+        }
+        long long know = 0;
+        for (int i = n - forget + 1; i <= n; i++)
+            know = (know + dp[i]) % MOD;
+        return (int)know;
+    }
+};