Create 1370.上升下降字符串.js

Author: yinxin630

1370.上升下降字符串.js

@@ -0,0 +1,30 @@
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var sortString = function(s) {
+    const chars = s.split('').sort((a, b) => a < b ? -1 : 1);
+    let result = [];
+    let count = chars.length;
+    let i = 0;
+    let di = 1;
+    let prev = '';
+    while (count) {
+        if (chars[i] && (prev === '' || chars[i] !== prev)) {
+            result.push(chars[i]);
+            prev = chars[i];
+            chars[i] = '';
+            count--;
+        }
+        i += di;
+        if (i === chars.length - 1) {
+            di = -1;
+            prev = '';
+        } else if (i === 0) {
+            di = 1;
+            prev = '';
+        }
+    }
+
+    return result.join('');
+};