Added kadane in rust (issue #104)

Rust/kadane.rs

@@ -0,0 +1,28 @@
+use std::cmp::max;
+
+/**
+ * Kadane's algorithm (O(n) time)
+ * Maximum Subarray Problem.
+ * dp[0] = arr[0]
+ * dp[i] = max(dp[i-1], 0) + arr[i]
+ */
+pub fn kadane(arr: &[i64]) -> i64 {
+    let mut dp: Vec<i64> = vec![0; arr.len()];
+    dp[0] = arr[0];
+    let mut mmax: i64 = dp[0];
+    for i in 1..arr.len() {
+        dp[i] = max(dp[i - 1], 0) + arr[i];
+        mmax = max(mmax, dp[i]);
+    }
+    return mmax;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn kadane_test() {
+        assert_eq!(kadane(&([-3, 1, -8, 12, 0, -3, 5, -9, 4])), 14);
+    }
+}