Merge pull request wangzheng0822#132 from nameczz/master

add [js] 15-16 binary find

javascript/15_binary/binaryFind.js

@@ -0,0 +1,27 @@
+/**
+ * 二分查找
+ *
+ * Author: nameczz
+ */
+// 数组必须有序 不存在重复
+const biaryFind = (sortedArr, target) => {
+    if (sortedArr.length === 0) return -1
+    let low = 0
+    let high = sortedArr.length - 1
+    while (low <= high) {
+        const mid = Math.floor((low + high) / 2)
+        if (target === sortedArr[mid]) {
+            return mid
+        } else if (target < sortedArr[mid]) {
+            high = mid - 1
+        } else {
+            low = mid + 1
+        }
+    }
+    return -1
+}
+const arr = [1, 4, 5, 6, 7, 8, 10, 11, 23, 42, 44, 54, 56, 77, 102]
+console.log(biaryFind(arr, 44))
+console.log(biaryFind(arr, 1))
+console.log(biaryFind(arr, 102))
+console.log(biaryFind(arr, 1111))

javascript/16_binary/binary-find.js

@@ -0,0 +1,90 @@
+/**
+ * 二分查找
+ *
+ * Author: nameczz
+ */
+
+
+// 查找第一个等于给定值
+const biaryFindFirst = (sortedArr, target) => {
+    if (sortedArr.length === 0) return -1
+    let low = 0
+    let high = sortedArr.length - 1
+    while (low <= high) {
+        const mid = Math.floor((low + high) / 2)
+
+        if (target < sortedArr[mid]) {
+            high = mid - 1
+        } else if (target > sortedArr[mid]) {
+            low = mid + 1
+        } else {
+            if (mid === 0 || sortedArr[mid - 1] < target) return mid
+            high = mid - 1
+        }
+    }
+    return -1
+}
+
+// 查找最后一个相等的数
+const biaryFindLast = (sortedArr, target) => {
+    if (sortedArr.length === 0) return -1
+    let low = 0
+    let high = sortedArr.length - 1
+    while (low <= high) {
+        const mid = Math.floor((low + high) / 2)
+        if (target < sortedArr[mid]) {
+            high = mid - 1
+        } else if (target > sortedArr[mid]) {
+            low = mid + 1
+        } else {
+            if (mid === sortedArr.length - 1 || sortedArr[mid + 1] > target) return mid
+            low = mid + 1
+        }
+    }
+    return -1
+}
+
+// 查找第一个大于等于给定值的元素
+const biaryFindFistBig = (sortedArr, target) => {
+    if (sortedArr.length === 0) return -1
+    let low = 0
+    let high = sortedArr.length - 1
+    while (low <= high) {
+        const mid = Math.floor((low + high) / 2)
+        if (target <= sortedArr[mid]) {
+            if (mid === 0 || sortedArr[mid - 1] < target) return mid
+            high = mid - 1
+        } else {
+            low = mid + 1
+        }
+    }
+    return -1
+}
+
+// 查找最后一个小于等于给定值的元素
+const biaryFindLastSmall = (sortedArr, target) => {
+    if (sortedArr.length === 0) return -1
+    let low = 0
+    let high = sortedArr.length - 1
+    while (low <= high) {
+        const mid = Math.floor((low + high) / 2)
+        if (sortedArr[mid] > target) {
+            high = mid - 1
+        } else {
+            if (mid === sortedArr.length - 1 || sortedArr[mid + 1] > target) return mid
+            low = mid + 1
+        }
+    }
+    return -1
+}
+
+const arr = [1, 2, 3, 4, 4, 4, 4, 4, 6, 7, 8, 8, 9]
+const first = biaryFindFirst(arr, 4)
+console.log(`FindFirst: ${first}`)
+
+const last = biaryFindLast(arr, 4)
+console.log(`FindLast: ${last}`)
+const FisrtBig = biaryFindFistBig(arr, 5)
+console.log(`FindFisrtBig: ${FisrtBig}`)
+const LastSmall = biaryFindLastSmall(arr, 4)
+console.log(`FindLastSmall: ${LastSmall}`)