Merge pull request doocs#32 from limbowandering/master

add javascript solutions

Author: yanglbme

solution/001.Two Sum/Solution.js

@@ -0,0 +1,11 @@
+const twoSum = function(nums, target) {
+  const map = {};
+
+  for (let i = 0; i < nums.length; i++) {
+    if (map[nums[i]] !== undefined) {
+      return [map[nums[i]], i]
+    } else {
+      map[target - nums[i]] = i
+    }
+  }  
+};

solution/007.Reverse Integer/Solution.js

@@ -0,0 +1,15 @@
+const reverse1 = function(x){
+  let s = String(x);
+  let isNegative = false;
+  if(s[0] === '-'){
+    isNegative = true;
+  }
+  s = parseInt(s.split('').reverse().join(''));
+  return isNegative ? (s > Math.pow(2,31) ? 0 : -s) : (s > Math.pow(2,31) - 1 ? 0 : s);
+}
+
+const reverse = function(x){
+  let result = parseInt(x.toString().split('').reverse().join(''));
+  if(result > Math.pow(2,31) - 1 || -result < Math.pow(-2,31)) return 0;
+  return x > 0 ? result: -result;
+}

solution/014.Longest Common Prefix/Solution.js

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+const longestCommonPrefix = function(strs){
+  if(strs.length === 0) return '';
+  for(let j = 0; j < strs[0].length; j++){
+    for(let i = 0; i < strs.length; i++){
+      if(strs[0][j] !== strs[i][j]){
+        return strs[0].substring(0,j);
+      }
+    }
+  }
+  return strs[0];
+}