change 5-10 to md

Author: BaffinLee

001-100/11. Container With Most Water.md

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+# 11. Container With Most Water
+
+- Difficulty: Medium.
+- Related Topics: Array, Two Pointers.
+- Similar Questions: Trapping Rain Water.
+
+## Problem
+
+Given *n* non-negative integers *a1*, *a2*, ..., *an*, where each represents a point at coordinate (*i*, *ai*). *n* vertical lines are drawn such that the two endpoints of line *i* is at (*i*, *ai*) and (*i*, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.
+
+Note: You may not slant the container and *n* is at least 2.
+
+
+## Solution
+
+```javascript
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+var maxArea = function(height) {
+  var max = 0;
+  var l = 0;
+  var r = height.length - 1;
+  while (l < r) {
+    max = Math.max(max, Math.min(height[l], height[r]) * (r - l));
+    if (height[l] < height[r]) {
+      l++;
+    } else {
+      r--;
+    }
+  }
+  return max;
+};
+```
+
+**Explain:**
+
+双指针从两头开始，判断哪边更高。积水量是矮的那边决定的，移动高的那边不可能提升积水量，所以移动矮的那边。
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1).

001-100/12. Integer to Roman.md

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+# 12. Integer to Roman
+
+- Difficulty: Medium.
+- Related Topics: Math, String.
+- Similar Questions: Roman to Integer, Integer to English Words.
+
+## Problem
+
+Roman numerals are represented by seven different symbols: ```I```, ```V```, ```X```, ```L```, ```C```, ```D``` and ```M```.
+
+```
+Symbol       Value
+I             1
+V             5
+X             10
+L             50
+C             100
+D             500
+M             1000
+```
+
+For example, two is written as ```II``` in Roman numeral, just two one's added together. Twelve is written as, ```XII```, which is simply ```X``` + ```II```. The number twenty seven is written as ```XXVII```, which is ```XX``` + ```V``` + ```II```.
+
+Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not ```IIII```. Instead, the number four is written as ```IV```. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as ```IX```. There are six instances where subtraction is used:
+
+- ```I``` can be placed before ```V``` (5) and ```X``` (10) to make 4 and 9. 
+- ```X``` can be placed before ```L``` (50) and ```C``` (100) to make 40 and 90. 
+- ```C``` can be placed before ```D``` (500) and ```M``` (1000) to make 400 and 900.
+
+Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.
+
+**Example 1:**
+
+```
+Input: 3
+Output: "III"
+```
+
+**Example 2:**
+
+```
+Input: 4
+Output: "IV"
+```
+
+**Example 3:**
+
+```
+Input: 9
+Output: "IX"
+```
+
+**Example 4:**
+
+```
+Input: 58
+Output: "LVIII"
+Explanation: C = 100, L = 50, XXX = 30 and III = 3.
+```
+
+**Example 5:**
+
+```
+Input: 1994
+Output: "MCMXCIV"
+Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
+```
+
+
+## Solution 1
+
+```javascript
+/**
+ * @param {number} num
+ * @return {string}
+ */
+var intToRoman = function(num) {
+  var str = [
+    ['I', 'V'],
+    ['X', 'L'],
+    ['C', 'D'],
+    ['M']
+  ];
+  var res = '';
+  var i = 0;
+  var tmp = 0;
+  while (num > 0) {
+    tmp = num % 10;
+    if (tmp === 9) {
+      res = str[i][0] + str[i + 1][0] + res;
+    } else if (tmp >= 5) {
+      res = str[i][1] + str[i][0].repeat(tmp - 5) + res;
+    } else if (tmp === 4) {
+      res = str[i][0] + str[i][1] + res;
+    } else {
+      res = str[i][0].repeat(tmp) + res;
+    }
+    num = Math.floor(num / 10);
+    i++;
+  }
+  return res;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(log(n)).
+* Space complexity : O(1).
+
+## Solution 2
+
+```javascript
+/**
+ * @param {number} num
+ * @return {string}
+ */
+var intToRoman = function(num) {
+  var map = [
+    [1, "I"],
+    [4, "IV"],
+    [5, "V"],
+    [9, "IX"],
+    [10, "X"],
+    [40, "XL"],
+    [50, "L"],
+    [90, "XC"],
+    [100, "C"],
+    [400, "CD"],
+    [500, "D"],
+    [900, "CM"],
+    [1000, "M"]
+  ];
+  var res = '';
+  var i = 12;
+  var tmp = 0;
+  while (num > 0) {
+    res += map[i][1].repeat(Math.floor(num / map[i][0]));
+    num %= map[i][0];
+    i--;
+  }
+  return res;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(log(n)).
+* Space complexity : O(1).
+
+## Solution 3
+
+```javascript
+/**
+ * @param {number} num
+ * @return {string}
+ */
+var intToRoman = function(num) {
+  var M =["", "M", "MM", "MMM"];
+  var C = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"];
+  var X = ["", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"];
+  var I = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"];
+  return M[Math.floor(num / 1000)]
+        + C[Math.floor((num % 1000) / 100)]
+        + X[Math.floor((num % 100) / 10)]
+        + I[num % 10];
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(1).
+* Space complexity : O(1).

001-100/13. Roman to Integer.md

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+# 13. Roman to Integer
+
+- Difficulty: Easy.
+- Related Topics: Math, String.
+- Similar Questions: Integer to Roman.
+
+## Problem
+
+Roman numerals are represented by seven different symbols: ```I```, ```V```, ```X```, ```L```, ```C```, ```D``` and ```M```.
+
+```
+Symbol       Value
+I             1
+V             5
+X             10
+L             50
+C             100
+D             500
+M             1000
+```
+
+For example, two is written as ```II``` in Roman numeral, just two one's added together. Twelve is written as, ```XII```, which is simply ```X``` + ```II```. The number twenty seven is written as ```XXVII```, which is ```XX``` + ```V``` + ```II```.
+
+Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not ```IIII```. Instead, the number four is written as ```IV```. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as ```IX```. There are six instances where subtraction is used:
+
+- ```I``` can be placed before ```V``` (5) and ```X``` (10) to make 4 and 9. 
+- ```X``` can be placed before ```L``` (50) and ```C``` (100) to make 40 and 90. 
+- ```C``` can be placed before ```D``` (500) and ```M``` (1000) to make 400 and 900.
+
+Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
+
+**Example 1:**
+
+```
+Input: "III"
+Output: 3
+```
+
+**Example 2:**
+
+```
+Input: "IV"
+Output: 4
+```
+
+**Example 3:**
+
+```
+Input: "IX"
+Output: 9
+```
+
+**Example 4:**
+
+```
+Input: "LVIII"
+Output: 58
+Explanation: C = 100, L = 50, XXX = 30 and III = 3.
+```
+
+**Example 5:**
+
+```
+Input: "MCMXCIV"
+Output: 1994
+Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
+```
+
+## Solution
+
+```javascript
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var romanToInt = function(s) {
+  var map = {
+    I: 1,
+    IV: 4,
+    V: 5,
+    IX: 9,
+    X: 10,
+    XL: 40,
+    L: 50,
+    XC: 90,
+    C: 100,
+    CD: 400,
+    D: 500,
+    CM: 900,
+    M: 1000
+  };
+  var len = s.length;
+  var i = 0;
+  var res = 0;
+  while (i < len) {
+    if (map[s.substr(i, 2)]) {
+      res += map[s.substr(i, 2)];
+      i += 2;
+    } else {
+      res += map[s[i]];
+      i += 1;
+    }
+  }
+  return res;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1).