Update 400. Nth Digit.java

futurus · web-flow · commit f81c27286355 · 2017-02-07T15:47:15.000-05:00
diff --git a/400. Nth Digit.java b/400. Nth Digit.java
@@ -30,3 +30,15 @@ public int findNthDigit(int n) {
         }
     }
 }
+
+// Space and Time improvement https://discuss.leetcode.com/topic/59378/short-python-java
+public int findNthDigit(int n) {
+    n -= 1;
+    int digits = 1, first = 1;
+    while (n / 9 / first / digits >= 1) {
+        n -= 9 * first * digits;
+        digits++;
+        first *= 10;
+    }
+    return (first + n/digits + "").charAt(n%digits) - '0';
+}

Original file line number	Diff line number	Diff line change
`@@ -30,3 +30,15 @@ public int findNthDigit(int n) {`
`30`	`30`	`}`
`31`	`31`	`}`
`32`	`32`	`}`
	`33`	`+`
	`34`	`+// Space and Time improvement https://discuss.leetcode.com/topic/59378/short-python-java`
	`35`	`+public int findNthDigit(int n) {`
	`36`	`+ n -= 1;`
	`37`	`+ int digits = 1, first = 1;`
	`38`	`+ while (n / 9 / first / digits >= 1) {`
	`39`	`+ n -= 9 * first * digits;`
	`40`	`+ digits++;`
	`41`	`+ first *= 10;`
	`42`	`+ }`
	`43`	`+ return (first + n/digits + "").charAt(n%digits) - '0';`
	`44`	`+}`