Merge pull request #14 from jtr109/1-two-sum

1 two sum

Author: jtr109

Cargo.lock

@@ -5,4 +5,5 @@ members = [
     "reverse_integer",
     "three_sum",
     "binary_tree_postorder_traversal",
+    "two_sum",
 ]

Cargo.toml

@@ -7,9 +7,11 @@ Resolving problems of LeetCode in RustLang.
 
 ## Solutions
 
+* [1. Two Sum](./two_sum/src/lib.rs)
 * [7. Reverse Integer](./reverse_integer/src/lib.rs)
 * [15. 3 Sum](./three_sum/src/lib.rs)
 * [215. Kth Largest Element in an Array](./kth_largest/src/lib.rs)
+* [145. Binary Tree Postorder Traversal](./binary_tree_postorder_traversal/src/lib.rs)
 
 ## Document
 

README.md

@@ -0,0 +1,9 @@
+[package]
+name = "two_sum"
+version = "0.1.0"
+authors = ["Ryan Li <conbas2019@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

two_sum/Cargo.toml

@@ -0,0 +1,58 @@
+/*!
+ * # 1. Two Sum
+ *
+ * * [Problem link](https://leetcode.com/problems/two-sum/)
+ */
+
+#![allow(dead_code)]
+
+struct Solution {}
+
+// ----------------------------------------------------------------------------
+#[derive(Eq, Ord, PartialOrd, PartialEq)]
+struct Number {
+    index: usize,
+    value: i32,
+}
+
+impl Number {
+    fn new(index: usize, value: i32) -> Self {
+        Number { index, value }
+    }
+}
+
+impl Solution {
+    pub fn two_sum(nums: Vec<i32>, target: i32) -> Vec<i32> {
+        let mut sorted = nums
+            .iter()
+            .enumerate()
+            .map(|(index, &value)| Number::new(index, value))
+            .collect::<Vec<Number>>();
+        sorted.sort_by(|a, b| a.value.cmp(&b.value));
+        let (mut low, mut high) = (0, sorted.len() - 1);
+        while low < high {
+            let s = sorted[low].value + sorted[high].value;
+            if s == target {
+                return vec![sorted[low].index as i32, sorted[high].index as i32];
+            } else if s < target {
+                low += 1;
+            } else {
+                high -= 1;
+            }
+        }
+        panic!("no match");
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_example() {
+        let nums = vec![2, 7, 11, 15];
+        let target = 9;
+        let expected = vec![0, 1];
+        assert_eq!(Solution::two_sum(nums, target), expected);
+    }
+}