add merge sort

Author: jamesmarva

code/examples/sort/src/lib.rs

@@ -0,0 +1,45 @@
+pub fn merge_sort_1(arr: &mut [i32]) {
+    let tmp = [0i32; (arr.len() - 1)];
+}
+fn merge_core(arr: &mut [i32], tmp: &mut [i32], start: usize, end: usize) {
+    if start >= end {
+        return;
+    }
+    let mid = start + ((end - start) >> 1);
+    merge_core(arr, tmp, start, mid);
+    merge_core(arr, tmp, mid + 1, end);
+    merge(arr, tmp, start, mid, end);
+}
+
+fn merge(arr: &mut [i32], tmp: &mut [i32], start: usize, mid: usize, end: usize) {
+    let mut i1 = start;
+    let mut i2 = mid + 1;
+    let mut i = 0;
+    while i1 <= mid && i2 <= end {
+        if arr[i1] <= arr[i2] {
+            tmp[i] = arr[i1];
+            i1+=1;
+        } else {
+            tmp[i] = arr[i2];
+            i2+=1;
+        }
+        i+=1;
+    }
+    while i1 <= mid {
+        tmp[i] = arr[i1];
+        i+=1;
+        i1+=1;
+    }
+    while i2 <= end {
+        tmp[i] = arr[i2];
+        i+=1;
+        i2+=1;
+    }
+
+    let len = i;
+    i = 0;
+    while i < len {
+        arr[start + i] = tmp[i];
+        i+=1;
+    }
+}

code/examples/sort/src/main.rs

@@ -1,6 +1,9 @@
+use sort::merge_sort_mod;
+
 fn main() {
     let mut a = [12,232,234,2,34,234,234,2,34,2,34,234,234,2,34,234,2,34,2,34,234,2,34,2];
-    quick(&mut a);
+    // quick(&mut a);
+    merge_sort_mod::merge_sort_1(&mut a);
     for item in &a {
         println!("{}", item);
     }