commit changes to gh-pages aug 18

Author: tg123

_includes/_root/gas-station/README.md

@@ -1,4 +1,14 @@
+## Guessing
 
-## TODO 
-  * write down thinking
+This problem is to find a UNIQUE station `i`, such that
 
+ * SUM(gas[0 .. i-1]) - SUM(cost[0 .. i-1]) + SUM(gas[i .. end]) - SUM(cost[i .. end]) >= 0
+ * SUM(gas[0 .. i-1]) - SUM(cost[0 .. i-1]) < 0
+
+`SUM(gas[0 .. i-1]) - SUM(cost[0 .. i-1]) < 0` is to guarantee that the `i` is unique.
+
+If `SUM(gas[0 .. i-1]) - SUM(cost[0 .. i-1]) < 0` and `SUM(gas[0 .. i-1]) - SUM(cost[0 .. i-1]) + SUM(gas[i .. end]) - SUM(cost[i .. end]) >= 0`, that is, `0 .. i-1` are all valid stations.
+
+## Brute force
+
+Just search through from `0` to `end`, find the valid `i`.

_includes/_root/permutations/README.md

@@ -1,4 +1,13 @@
+## Definition
+
+
+```
+
+permute(num) = empty                                num is empty
+               num                                  num has only one element
+               n + permute(num - n)    [n in num]   otherwise
+               
+```
+
 
-## TODO 
-  * write down thinking
 

gas-station/index.md

@@ -1,7 +1,8 @@
 ---
 layout: solution
 title: Gas Station
-date: 2014-07-23 02:42:48 +0800
+date: 2014-08-17 23:57:14 +0800
+eaten: true
 ---
 {% assign leetcode_name = {{page.path | remove: '/index.md'}}  %}
 {% assign leetcode_readme = {{leetcode_name | append: '/README.md' | prepend: '_root/' }}  %}

permutations/index.md

@@ -1,7 +1,8 @@
 ---
 layout: solution
 title: Permutations
-date: 2014-07-31 12:08:12 +0800
+date: 2014-08-17 23:07:06 +0800
+eaten: true
 ---
 {% assign leetcode_name = {{page.path | remove: '/index.md'}}  %}
 {% assign leetcode_readme = {{leetcode_name | append: '/README.md' | prepend: '_root/' }}  %}