Merge pull request kothariji#593 from Hilbertmf/master

create (LEETCODE)search-in-rotated-sorted-array.cpp

Author: kothariji

Searching/(LEETCODE)search-in-rotated-sorted-array.cpp

@@ -0,0 +1,92 @@
+// https://leetcode.com/problems/search-in-rotated-sorted-array/
+class Solution {
+public:
+    
+  int calcMid(int left, int right) {
+    return left + (right - left)/2;
+  }
+  
+  bool isBorder(vector<int>& nums, int i) {
+    if(nums[i] > nums[i+1])
+      return true;
+    return false;
+  }
+
+  int binarySearch(vector<int>& nums, int left, int right, int target) {
+    int i = calcMid(left, right);
+    while(nums[i] != target) {
+      if(nums[i] < target)
+        left = i;
+      else
+        right = i;
+      
+      i = calcMid(left, right);
+      if(right - left < 2 && nums[i] != target) {
+        if(nums[left] == target)
+          return left;
+        else if(nums[right] == target)
+          return right;
+        else {
+          i = -1;
+          break;  
+        }
+      }
+    }
+    return i;
+  }
+  
+  int findArrayBorder(vector<int>& nums, int left, int right) {
+    int firstListMax = nums[nums.size()-1];
+    int i = calcMid(left, right);
+    while(!isBorder(nums, i)) {
+      if(nums[i] < firstListMax)
+        right = i;
+      else
+        left = i;
+      
+      i = calcMid(left, right);
+    }
+    return i;
+  }
+
+  int search(vector<int>& nums, int target) {
+    // edge cases:
+    if(target == nums[nums.size()-1])
+      return nums.size()-1;
+    if(target == nums[0])
+      return 0;
+    if(nums.size() == 1)
+      return -1;
+    
+    int length = nums.size();
+    int firstListBegin = 0, firstListEnd;
+    int secondListBegin, secondListEnd = length - 1;
+    int targetIdx = -1;
+    
+    //check whether the array has been rotated
+    if(nums[0] > nums[length-1]) {
+      firstListEnd = findArrayBorder(nums, 0, length-1);
+      secondListBegin = firstListEnd + 1;
+      
+      //edge case
+      if(secondListBegin == secondListEnd) {
+        if(target == nums[secondListBegin])
+          return secondListBegin;
+        targetIdx = binarySearch(nums, 0, firstListEnd, target);
+      }
+      else if(target <= nums[secondListEnd]) {
+        // list 2
+        targetIdx = binarySearch(nums, secondListBegin, secondListEnd, target);
+      }
+      else {
+        // list 1
+        targetIdx = binarySearch(nums, 0, firstListEnd, target);
+      }
+    }
+    else {
+      targetIdx = binarySearch(nums, 0, length - 1, target);
+    } 
+    
+    return targetIdx;
+  }
+};