feat : find-minimum-in-rotated-sorted-array

Author: ekgns33

find-minimum-in-rotated-sorted-array/ekgns33.java

@@ -0,0 +1,56 @@
+/**
+ input : array of integers
+ output : minimum element's value
+
+ 3 4 5 1 2
+ draw graph
+
+ 5
+ 4
+ 3
+ 2
+ 1
+ l    r
+ l    r
+ l            r
+ --------------
+ 5
+ 4
+ 3
+ 2
+ 1
+ mid  right
+ --------------
+ left < right ->> sorted.
+ left < mid ->>  don't have to search range [left, mid]
+ mid > right ->> rotation point is between [mid, right];
+
+ solution 1) brute force
+ read the array
+
+ tc : O(n)
+ sc : O(1);
+
+ solution 2) binary search
+ do binary search, move pointers with descripted conditions
+ after binary search loop ends, the left pointer is the minimum element
+
+ tc : O(logn)
+ sc : O(1)
+ */
+
+class Solution {
+  public int findMin(int[] nums) {
+    int l = 0;
+    int r = nums.length - 1;
+    while(l < r) {
+      int mid = (r - l) / 2 + l;
+      if(nums[mid] < nums[r]) {
+        r = mid;
+      } else {
+        l = mid + 1;
+      }
+    }
+    return nums[l];
+  }
+}