Merge branch 'master' of https://github.com/sl1673495/frontend-code-fragment

Author: sl1673495

算法/有序数组求交集.js

@@ -0,0 +1,79 @@
+var a = []
+
+for (let index = 0; index < 500; index++) {
+  a.push(i)
+}
+
+for (var i = 16; i < 10000; i++) {
+  a.push(i)
+}
+
+var b = []
+
+for (let index = 0; index < 500; index++) {
+  b.push(i)
+}
+
+for (var i = 10001; i < 50000; i++) {
+  b.push(i)
+}
+
+function mapIntersection(arr1, arr2) {
+  console.time()
+  var map = new Map()
+  for (var i = 0; i < arr1.length; i++) {
+    map.set(arr1[i], true)
+  }
+
+  var result = []
+  for (var i = 0; i < arr2.length; i++) {
+    var val = arr2[i]
+    if (map.get(val)) {
+      result.push(val)
+    }
+  }
+  console.timeEnd()
+  return result
+}
+
+console.log("mapIntersection", mapIntersection(a, b))
+
+function pointIntersection(arr1, arr2) {
+  console.time()
+  let i = 0
+  let j = 0
+
+  let l1 = arr1.length
+  let l2 = arr2.length
+
+  let result = []
+  while (i < l1 && j < l2) {
+    let val1 = arr1[i]
+    let val2 = arr2[j]
+    let val1Last = arr1[i - 1]
+    let val2Last = arr2[j - 1]
+
+    if (val1 > val2) {
+      i++
+    }
+
+    if (val1 === val2) {
+      result.push(val1)
+      i++
+      j++
+    }
+
+    if (val1 < val2) {
+      j++
+    }
+
+    if (val1 > val2Last || val2 > val1Last) {
+      console.timeEnd()
+      return result
+    }
+  }
+  console.timeEnd()
+  return result
+}
+
+console.log('pointIntersection', pointIntersection(a, b))

算法/有序数组的单个元素-540.js

@@ -0,0 +1,61 @@
+/**
+  540. 有序数组中的单一元素
+  给定一个只包含整数的有序数组，每个元素都会出现两次，唯有一个数只会出现一次，找出这个数。
+
+  示例 1:
+
+  输入: [1,1,2,3,3,4,4,8,8]
+  输出: 2
+  示例 2:
+
+  输入: [3,3,7,7,10,11,11]
+  输出: 10
+  注意: 您的方案应该在 O(log n)时间复杂度和 O(1)空间复杂度中运行。
+ */
+
+function singleNonDuplicate(nums) {
+  let len = nums.length
+
+  let lo = 0
+  let hi = len - 1
+
+  while (lo < hi) {
+    let mid = lo + Math.floor((hi - lo) / 2)
+    let midVal = nums[mid]
+
+    // 被mid后的数组长度是奇数还是偶数
+    let halvesAreEven = (hi - mid) % 2 == 0;
+    if (midVal === nums[mid - 1]) {
+      if (halvesAreEven) {
+        // [0, 1, 1, 2, 2]
+        //       mid
+        // 显然左边是奇数 [0] hi是mid往左两位
+        hi = mid - 2
+      }else {
+        // [0, 0, 1, 1, 2, 2, 3]
+        //          mid
+        // 显然右边是奇数 [2, 2, 3] lo是mid往右一位
+        lo = mid + 1
+      }
+
+    }else if (midVal === nums[mid + 1]) {
+      if (halvesAreEven) {
+        // [0, 0, 1, 1, 2]
+        //       mid
+        // 右边是奇数 [2] lo是mid右移动两位
+        lo = mid + 2
+      }else {
+         // [0, 0, 1, 2, 2, 3, 3]
+         //          mid
+         // 左边是奇数 [0, 0, 1] hi是mid左移一位
+         hi = mid - 1
+      }
+    } else {
+      return midVal
+    }
+  }
+  return nums[lo]
+}
+
+
+console.log(singleNonDuplicate([3,3,7,7,10,11,11]))