add: 3Sum

Author: hijiangtao

README.md

@@ -16,6 +16,7 @@ This is the solutions collection of my LeetCode submissions, most of them are pr
 |11|[Container With Most Water](https://leetcode.com/problems/container-with-most-water/) | [JavaScript](./src/container-with-most-water/res.js)|Medium|
 |13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer/) | [JavaScript](./src/roman-to-integer/res.js)|Easy|
 |14|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/) | [JavaScript](./src/longest-common-prefix/res.js)|Easy|
+|15|[3Sum](https://leetcode.com/problems/3sum/) | [JavaScript](./src/3sum/res.js) |Medium|
 |17|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) | [JavaScript](./src/letter-combinations-of-a-phone-number/res.js)|Medium|
 |19|[Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/) | [JavaScript](./src/remove-nth-node-from-end-of-list/res.js)|Medium|
 |22|[Generate Parentheses](https://leetcode.com/problems/generate-parentheses/) | [JavaScript](./src/generate-parentheses/res.js)|Medium|

src/3sum/res.js

@@ -0,0 +1,55 @@
+/**
+ * res.js
+ * @authors Joe Jiang ([email protected])
+ * @date    2017-04-03 23:45:47
+ * 
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+let threeSum = function(nums) {
+	nums.sort(function(a, b) {
+		return a - b;
+	});
+
+	let numlen = nums.length,
+		end = nums[numlen - 1],
+		eInd = numlen - 2,
+		res = [];
+
+	if (numlen < 3 || nums[0] > 0 || end < 0) {
+		return [];
+	}
+
+	for (let i = 0; i < eInd; i++) {
+		let revi = -nums[i],
+			j = i + 1,
+			k = numlen - 1;
+
+		if (revi < 0) {
+			break;
+		}
+
+		while (j < k) {
+			let norj = nums[j],
+				nork = nums[k];
+			if (norj + nork > revi) {
+				k--;
+			} else if (norj + nork < revi) {
+				j++;
+			} else {
+				res.push([nums[i], nums[j], nums[k]]);
+
+				//   forbid duplicated numbers
+				while (j + 1 < numlen && nums[j] === nums[j + 1]) j++;
+				while (nums[k] === nums[k - 1]) k--;
+				k--;
+				j++;
+
+			}
+		}
+
+		while (i + 1 < numlen && nums[i] === nums[i + 1]) i++;
+	}
+
+	return res;
+};

src/longest-common-prefix/res.js

@@ -10,35 +10,35 @@
  * @return {string}
  */
 let longestCommonPrefix = function(strs) {
-    if (strs === '' || strs.length === 0) {
-        return '';
-    }
-    
-    let prefix = '',
-        strslen = strs.length,
-        strlen = strs[0].length;
-        
-    for (let i=0; i < strlen; i++) {
-        let jud = true;
-        
-        for (let j=1; j<strslen; j++) {
-            if (strs[j][i] === undefined || strs[j][i] !== strs[0][i]) {
-                jud = false;
-                break;
-            }
-        }
-        
-        if (jud) {
-            prefix += strs[0][i];
-        } else {
-            return prefix;
-        }
-    }
-    
-    return prefix;
+	if (strs === '' || strs.length === 0) {
+		return '';
+	}
+
+	let prefix = '',
+		strslen = strs.length,
+		strlen = strs[0].length;
+
+	for (let i = 0; i < strlen; i++) {
+		let jud = true;
+
+		for (let j = 1; j < strslen; j++) {
+			if (strs[j][i] === undefined || strs[j][i] !== strs[0][i]) {
+				jud = false;
+				break;
+			}
+		}
+
+		if (jud) {
+			prefix += strs[0][i];
+		} else {
+			return prefix;
+		}
+	}
+
+	return prefix;
 };
 
 /**
  * Another solution: Sort the array first, and then you can simply compare the first and last elements in the sorted array.
  * 
- */
+ */

src/permutations/res.js

@@ -9,39 +9,39 @@
  * @return {number[][]}
  */
 let permute = function(nums) {
-    let numlen = nums.length,
-        res = [];
-        
-    if (numlen === 0) {
-        return res;
-    } else if (numlen === 1) {
-        res.push(nums);
-        return res;
-    }
-    
-    return subpermute([], nums);
+	let numlen = nums.length,
+		res = [];
+
+	if (numlen === 0) {
+		return res;
+	} else if (numlen === 1) {
+		res.push(nums);
+		return res;
+	}
+
+	return subpermute([], nums);
 };
 
 let subpermute = function(base, nums) {
-    let numlen = nums.length,
-        res = [];
-        
-    if (numlen === 1) {
-        return [ base.concat(nums) ];
-    }
-    
-    for (let i=0; i<numlen; i++) {
-        let subarray = [];
-        for (let j=0; j<numlen; j++) {
-            if (i===j) {
-                continue;
-            }
-            subarray.push(nums[j]);
-        }
-        
-        let newbase = base.concat( [nums[i]] );
-        res = res.concat( subpermute(newbase, subarray) );
-    }
-    
-    return res;
-};
+	let numlen = nums.length,
+		res = [];
+
+	if (numlen === 1) {
+		return [base.concat(nums)];
+	}
+
+	for (let i = 0; i < numlen; i++) {
+		let subarray = [];
+		for (let j = 0; j < numlen; j++) {
+			if (i === j) {
+				continue;
+			}
+			subarray.push(nums[j]);
+		}
+
+		let newbase = base.concat([nums[i]]);
+		res = res.concat(subpermute(newbase, subarray));
+	}
+
+	return res;
+};

src/string-to-integer-atoi/res.js

@@ -9,43 +9,43 @@
  * @return {number}
  */
 let myAtoi = function(str) {
-   const INT_MAX = 2147483647,
-        INT_MIN = -2147483648,
-        bound = Number.parseInt(INT_MAX/10);
-   let strlen = str.length,
-       signal = 1, // 1 stands for positive number, 0 stands for negative number
-       res = 0;
-   
-   while (str[0] && str[0] === ' ') {
-       str = str.slice(1);
-       strlen -= 1;
-   }
-   
-   if (strlen === 0) {
-       return 0;
-   }
-   
-   if(str[0] === '-') {
-       signal = 0;
-       str = str.slice(1);
-   } else if (str[0] === "+") {
-       str = str.slice(1);
-   }
-   
-   while (str[0] >= '0' && str[0] <= '9') {
-    //   console.log(str[0]);
-       let element = Number.parseInt(str[0]);
-       
-       if ( res>bound || (res===bound && element>7) ) {
-           if(signal) {
-               return INT_MAX;
-           }
-           return INT_MIN;
-       }
-       
-       res = res * 10 + element;
-       str = str.slice(1);
-   }
-   
-   return signal? res:-res;
-};
+	const INT_MAX = 2147483647,
+		INT_MIN = -2147483648,
+		bound = Number.parseInt(INT_MAX / 10);
+	let strlen = str.length,
+		signal = 1, // 1 stands for positive number, 0 stands for negative number
+		res = 0;
+
+	while (str[0] && str[0] === ' ') {
+		str = str.slice(1);
+		strlen -= 1;
+	}
+
+	if (strlen === 0) {
+		return 0;
+	}
+
+	if (str[0] === '-') {
+		signal = 0;
+		str = str.slice(1);
+	} else if (str[0] === "+") {
+		str = str.slice(1);
+	}
+
+	while (str[0] >= '0' && str[0] <= '9') {
+		//   console.log(str[0]);
+		let element = Number.parseInt(str[0]);
+
+		if (res > bound || (res === bound && element > 7)) {
+			if (signal) {
+				return INT_MAX;
+			}
+			return INT_MIN;
+		}
+
+		res = res * 10 + element;
+		str = str.slice(1);
+	}
+
+	return signal ? res : -res;
+};