update 3 leetcode

Author: kyriejoshua

leetcode/1.two-sum.js

@@ -0,0 +1,25 @@
+/*
+ * @lc app=leetcode id=1 lang=javascript
+ *
+ * [1] Two Sum
+ */
+
+// @lc code=start
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function(nums, target) {
+ for (let i = 0; i < nums.length - 1; i++) {
+ for (let j = i + 1; j < nums.length; j++) {
+ const ei = nums[i];
+ const ej = nums[j];
+ if (ej + ei === target) {
+ return [i, j]
+ }
+ }
+ }
+};
+
+// @lc code=end

leetcode/35.search-insert-position.js

@@ -0,0 +1,31 @@
+/*
+ * @lc app=leetcode id=35 lang=javascript
+ *
+ * [35] Search Insert Position
+ */
+
+// @lc code=start
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number}
+ */
+var searchInsert = function(nums, target) {
+ const len = nums.length;
+ let left = 0, right = len - 1, ans = len;
+ // 二分法向中间查找
+ // 不是两边往中间找，而是不断更新中间值
+ while (left <= right) {
+ // 二进制右移一位，等同于对半取整，因为向左一位是乘以 2， 向右一位是除以 2
+ let mid = ((right - left) >> 1) + left;
+ if (target <= nums[mid]) {
+ ans = mid;
+ right = mid - 1;
+ } else {
+ left = mid + 1;
+ }
+ }
+ return ans;
+};
+searchInsert([1,3,5,6], 2);
+// @lc code=end

leetcode/7.reverse-integer.js

@@ -0,0 +1,41 @@
+/*
+ * @lc app=leetcode id=7 lang=javascript
+ *
+ * [7] Reverse Integer
+ */
+
+// @lc code=start
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var reverse = function(x) {
+ // 是否是 负数
+ let f = x < 0;
+ // 转成字符串，再用数组反序
+ let newX = +(Math.abs(x).toString().split('').reverse().join(''));
+ newX = f ? -1 * newX : newX;
+ if (Math.pow(-2, 31) > newX || (Math.pow(2, 31) - 1) < newX) {
+ return 0;
+ }
+ return newX;
+};
+
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var reverseMath = function(x) {
+ // 数学的方法 每一位相除
+ let res = 0;
+ while (x) {
+ const digit = x % 10;
+ x = ~~(x / 10);
+ res = digit + res * 10;
+ if (Math.pow(-2, 31) > res || (Math.pow(2, 31) - 1) < res) {
+ return 0;
+ }
+ }
+ return res;
+};
+// @lc code=end