maximum subarray solution

Author: yhkee0404

maximum-subarray/yhkee0404.rs

@@ -0,0 +1,35 @@
+impl Solution {
+    pub fn max_sub_array(nums: Vec<i32>) -> i32 {
+        return Self::solve(&nums, 0, nums.len()).unwrap_or(0);
+    }
+    fn solve(nums: &Vec<i32>, l: usize, r: usize) -> Option<i32> {
+        if l >= r {
+            return None
+        }
+        if l + 1 == r {
+            return Some(nums[l])
+        }
+        let mid = l + ((r - l) >> 1);
+        let a = Self::solve(nums, l, mid);
+        let b = Self::solve(nums, mid, r);
+        if a.is_none() || b.is_none() {
+            return a.or(b)
+        }
+        let mut ans = a.max(b);
+        let mut c = 0;
+        let mut d = 0;
+        for i in (l..mid).rev() {
+            c += nums[i];
+            d = d.max(c);
+        }
+        if d == 0 {
+            return ans
+        }
+        c = d;
+        for i in mid..r {
+            c += nums[i];
+            d = d.max(c);
+        }
+        ans.max(Some(d))
+    }
+}