Create 1269. Number of Ways to Stay in the Same Place After Some Steps.cpp

Author: Yashmenaria1

1269. Number of Ways to Stay in the Same Place After Some Steps.cpp

@@ -0,0 +1,26 @@
+class Solution {
+    int mod = pow(10, 9) + 7;
+    vector<int> ways{0, -1, 1};
+    vector<vector<int>> dp;
+public:
+    int numWays(int n, int len) {
+        dp.resize(n+1, vector<int>((n)/2 + 1, -1));
+        return solve(n, len);
+    }
+    
+    int solve(int n, int len, int pos = 0) {
+        if(n == 0 && pos == 0) return 1;
+        
+        if(pos < 0 || pos >= len || n == 0 || pos > n) return 0;
+        
+        if(dp[n][pos] != -1) return dp[n][pos];
+        
+        int ans = 0;
+        for(int i=0; i<3; i++) {
+            ans = (ans % mod + solve(n-1, len, pos + ways[i]) % mod) % mod;
+        }
+        
+        return dp[n][pos] = ans % mod;
+        
+    }
+};