Update 1639-number-of-ways-to-form-a-target-string-given-a-dictionary.js

Author: everthis

1639-number-of-ways-to-form-a-target-string-given-a-dictionary.js

@@ -1,3 +1,31 @@
+/**
+ * @param {string[]} words
+ * @param {string} target
+ * @return {number}
+ */
+const numWays = function (words, target) {
+  const m = words[0].length, len = words.length
+  const n = target.length, a = 'a'.charCodeAt(0)
+  const mod = 10 ** 9 + 7
+  const dp = Array(n).fill(0)
+  for(let i = 0; i < m; i++) {
+    const freq = Array(26).fill(0)
+    for(let j = 0; j < len; j++) {
+      freq[words[j].charCodeAt(i) - a]++
+    }
+    for(let j = Math.min(i, n - 1); j >= 0; j--) {
+      const code = target[j].charCodeAt(0) - a
+      if(freq[code] > 0) {
+        dp[j] += (j === 0 ? freq[code] : dp[j - 1] * freq[code])
+        dp[j] %= mod
+      }
+    }
+  }
+  return dp[n - 1]
+}
+
+// another
+
 /**
  * @param {string[]} words
  * @param {string} target