Add solution #1155

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,155 LeetCode solutions in JavaScript
+# 1,156 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -903,6 +903,7 @@
 1146|[Snapshot Array](./solutions/1146-snapshot-array.js)|Medium|
 1147|[Longest Chunked Palindrome Decomposition](./solutions/1147-longest-chunked-palindrome-decomposition.js)|Hard|
 1154|[Day of the Year](./solutions/1154-day-of-the-year.js)|Easy|
+1155|[Number of Dice Rolls With Target Sum](./solutions/1155-number-of-dice-rolls-with-target-sum.js)|Medium|
 1161|[Maximum Level Sum of a Binary Tree](./solutions/1161-maximum-level-sum-of-a-binary-tree.js)|Medium|
 1189|[Maximum Number of Balloons](./solutions/1189-maximum-number-of-balloons.js)|Easy|
 1200|[Minimum Absolute Difference](./solutions/1200-minimum-absolute-difference.js)|Easy|

solutions/1155-number-of-dice-rolls-with-target-sum.js

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+/**
+ * 1155. Number of Dice Rolls With Target Sum
+ * https://leetcode.com/problems/number-of-dice-rolls-with-target-sum/
+ * Difficulty: Medium
+ *
+ * You have n dice, and each dice has k faces numbered from 1 to k.
+ *
+ * Given three integers n, k, and target, return the number of possible ways (out of the kn total
+ * ways) to roll the dice, so the sum of the face-up numbers equals target. Since the answer may
+ * be too large, return it modulo 109 + 7.
+ */
+
+/**
+ * @param {number} n
+ * @param {number} k
+ * @param {number} target
+ * @return {number}
+ */
+var numRollsToTarget = function(diceCount, faceCount, targetSum) {
+  const MOD = 1e9 + 7;
+  let dp = new Array(targetSum + 1).fill(0);
+  dp[0] = 1;
+
+  for (let dice = 1; dice <= diceCount; dice++) {
+    const nextDp = new Array(targetSum + 1).fill(0);
+    for (let sum = 1; sum <= targetSum; sum++) {
+      for (let face = 1; face <= faceCount && face <= sum; face++) {
+        nextDp[sum] = (nextDp[sum] + dp[sum - face]) % MOD;
+      }
+    }
+    dp = nextDp;
+  }
+
+  return dp[targetSum];
+};