Create 115-distinct-subsequences.js

Author: everthis

115-distinct-subsequences.js

@@ -0,0 +1,25 @@
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {number}
+ */
+const numDistinct = function(s, t) {
+  const tlen = t.length
+  const slen = s.length
+  const mem = Array.from({ length: tlen + 1 }, () =>
+    new Array(slen + 1).fill(0)
+  )
+  for (let j = 0; j <= slen; j++) {
+    mem[0][j] = 1
+  }
+  for (let i = 0; i < tlen; i++) {
+    for (let j = 0; j < slen; j++) {
+      if (t.charAt(i) === s.charAt(j)) {
+        mem[i + 1][j + 1] = mem[i][j] + mem[i + 1][j]
+      } else {
+        mem[i + 1][j + 1] = mem[i + 1][j]
+      }
+    }
+  }
+  return mem[tlen][slen]
+}