'1'

notes/src/day1/lc704.md

@@ -19,3 +19,66 @@
 
 ## 解题思路
 
+直接使用标准库的做法，slice的partition_point没有找到的时候返回数组的长度
+
+```rust
+impl Solution {
+    pub fn search(nums: Vec<i32>, target: i32) -> i32 {
+        let x = nums.partition_point(|&x| x < target);
+        if x == nums.len() { return -1 }
+        if nums[x] == target { return x as i32 }
+        -1
+    }
+}
+```
+
+手写的二分查找
+
+```rust
+impl Solution {
+    pub fn search(nums: Vec<i32>, target: i32) -> i32 {
+        let mut left = 0;
+        let mut right = nums.len();
+        while left < right {
+            let mid = left + (right - left) / 2;
+            if nums[mid] < target {
+                left = mid + 1
+            } else if nums[mid] > target {
+                right = mid;
+            } else {
+                return mid as i32
+            }
+        }
+        -1
+    }
+}
+```
+
+
+## 学习感想
+
+对区间的定义没有想清楚，**区间的定义就是不变量**，在操作的过程中 保持不变量
+
+在左闭右闭区间的情况下 由于right 要 -1，所以要考虑right=0 - 1的情况
+
+```rust
+
+impl Solution {
+    pub fn search(nums: Vec<i32>, target: i32) -> i32 {
+        let mut left = 0isize;
+        let mut right = nums.len() as isize - 1;
+        while left <= right {
+            let mid = (left + (right - left) / 2) as usize;
+            if nums[mid] < target {
+                left = mid as isize + 1
+            } else if nums[mid] > target {
+                right = mid as isize - 1;
+            } else {
+                return mid as i32
+            }
+        }
+        -1
+    }
+}
+```
+