Merge pull request #635 from Priyasingh6304/patch-1

ADD new solution7th October LeetCode Solution.cpp

Author: akkupy

LeetCodeQuestions/7th October LeetCode Solution.cpp

@@ -0,0 +1,38 @@
+class Solution {
+ public:
+  int numOfArrays(int n, int m, int k) {
+    constexpr int kMod = 1'000'000'007;
+    // dp[i][j][k] := # of ways to build an array of length i, where j is the
+    // Max used num and k is the search_cost
+    vector<vector<vector<int>>> dp(
+        n + 1, vector<vector<int>>(m + 1, vector<int>(k + 1)));
+
+    for (int j = 1; j <= m; ++j)
+      dp[1][j][1] = 1;
+
+    for (int i = 2; i <= n; ++i)                 // For each length
+      for (int j = 1; j <= m; ++j)               // For each max value
+        for (int cost = 1; cost <= k; ++cost) {  // For each cost
+          // 1. appending any of [1, j] in i-th position
+          //    doesn't change the max and cost
+          dp[i][j][cost] = static_cast<long>(j) * dp[i - 1][j][cost] % kMod;
+          // 2. appending j in i-th position
+          //    make j the new max and cost 1
+          for (int prevMax = 1; prevMax < j; ++prevMax) {
+            dp[i][j][cost] += dp[i - 1][prevMax][cost - 1];
+            dp[i][j][cost] %= kMod;
+          }
+        }
+
+    int ans = 0;
+    for (int j = 1; j <= m; ++j) {
+      ans += dp[n][j][k];
+      ans %= kMod;
+    }
+    return ans;
+  }
+};
+
+//Leetcode POTD
+//CPP
+//7th Oct