Count say

Author: crisdosaygo

coding/leetcode/38-count-say.js

@@ -0,0 +1,38 @@
+const DEBUG = false;
+
+var countAndSay = function(n) {
+  let i = n - 1;
+  n = "1";
+  while(i--) {
+    n = nextCS(n);
+  }
+  return n;
+};
+
+function nextCS(n) {
+  const runs = Array.from(n).reduce((R, char) => {
+    let run = R.pop(); 
+
+    if ( run && (run.char !== char) ) {
+      R.push(run);
+      run = null;
+    } 
+
+    if ( ! run ) {
+      run = {
+        char,
+        count: 0
+      };
+    } 
+
+    run.count++;      
+
+    R.push(run);
+
+    return R;
+  }, []);
+  DEBUG && console.log(runs);
+  return runs.reduce((S, {char,count}) => S + `${count}${char}`, '');
+}
+
+console.log(countAndSay(5));