1

Author: Ainevsia

notes/src/day2/lc209.md

@@ -101,3 +101,59 @@ impl Solution {
 
 所以这个引用就不要自动匹配掉了，就手动解引用吧
 
+
+思路：前缀和+双指针
+
+```rust
+# struct Solution {}
+impl Solution {
+    pub fn min_sub_array_len(target: i32, nums: Vec<i32>) -> i32 {
+        // prefix sum
+        let pre_sum: Vec<i32> = nums.iter().scan(0i32, |st, &x| {
+            *st += x;
+            Some(*st)
+        }).collect();
+        let idx: usize = pre_sum.partition_point(|&x| x < target);
+        if idx == nums.len() { return 0i32 }
+        let mut res: usize = idx + 1usize;
+        let mut right: usize = idx;
+        let mut left: usize = 0usize;
+        while right < nums.len() {
+            while pre_sum[right] - pre_sum[left] >= target {
+                left += 1usize;
+            }
+            let candidate: usize = right - left + 1usize;
+            res = std::cmp::min(candidate, res);
+            right += 1usize;
+        }
+        res as i32
+    }
+}
+```
+
+
+
+```rust
+
+# struct Solution {}
+
+impl Solution {
+    pub fn min_sub_array_len(target: i32, nums: Vec<i32>) -> i32 {
+        let mut sum: i32 = 0i32;
+        let mut left: usize = 0usize;
+        let mut res: usize = usize::MAX;
+        for right in 0usize..nums.len() {
+            sum += nums[right];
+            while sum >= target {
+                res = std::cmp::min(res, right - left + 1usize);
+                sum -= nums[left];
+                left += 1usize;
+            }
+        }
+        match res {
+            usize::MAX => 0,
+            _ => res as i32,
+        }
+    }
+}
+```