leetcode 81

leetcode/81/81.go

@@ -0,0 +1,35 @@
+func BinarySearch(nums []int, l, r, target int) int {
+    if l == r && nums[l] == target {
+        return l
+    } else if l > r || ( l == r && nums[l] != target)  {
+        return -1
+    }
+
+    mid := (l + r) / 2
+    // 判断区间类型
+    if nums[l] >= nums[r] {
+        // 旋转区间
+        if nums[mid] == target {
+            return mid
+        }
+        // 两侧区间都需要搜索
+        if pos := BinarySearch(nums, l, mid-1, target); pos != -1 {
+            return pos
+        }
+        return BinarySearch(nums, mid+1, r, target)
+    } else {
+        // 有序区间
+        if nums[mid] == target {
+            return mid
+        } else if nums[mid] > target {
+            // 左侧
+            return BinarySearch(nums, l, mid-1, target)
+        } else {
+            return BinarySearch(nums, mid+1, r, target)
+        }
+    }
+}
+
+func search(nums []int, target int) bool {
+    return BinarySearch(nums, 0, len(nums)-1, target) != -1
+}