Find Minimum in Rotated Sorted Array II

haoel · haoel · commit f3428f9a26a1 · 2014-10-21T14:43:51.000+08:00
diff --git a/README.md b/README.md
@@ -5,6 +5,7 @@ LeetCode C++ Solutions
 
 | Title | Solution | Add Date | Difficulty |
 | ----- | -------- | -------- | ---------- |
+|[Find Minimum in Rotated Sorted Array II](https://oj.leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/)| [C++](./src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.II.cpp)|2014/10/20|Hard|
 |[Find Minimum in Rotated Sorted Array](https://oj.leetcode.com/problems/find-minimum-in-rotated-sorted-array/)| [C++](./src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.cpp)|2014/10/15|Medium|
 |[Maximum Product Subarray](https://oj.leetcode.com/problems/maximum-product-subarray/)| [C++](./src/maximumProductSubarray/maximumProductSubarray.cpp)|2014/9/23|Medium|
 |[Reverse Words in a String](https://oj.leetcode.com/problems/reverse-words-in-a-string/)| [C++](./src/reverseWordsInAString/reverseWordsInAString.cpp)|2014/3/5|Medium|
diff --git a/src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.II.cpp b/src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.II.cpp
@@ -0,0 +1,146 @@
+// Source : https://oj.leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/
+// Author : Hao Chen
+// Date   : 2014-10-21
+
+/********************************************************************************** 
+* 
+* Follow up for "Find Minimum in Rotated Sorted Array":
+* What if duplicates are allowed?
+* 
+* Would this affect the run-time complexity? How and why?
+* 
+* Suppose a sorted array is rotated at some pivot unknown to you beforehand.
+* 
+* (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).
+* 
+* Find the minimum element.
+* 
+* The array may contain duplicates.
+*               
+**********************************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+
+
+/*
+ * Need be very careful for the following cases:
+ *
+ *    [3, 3, 3, 3, 3]
+ *  
+ *    [3, 3, 3, 1, 3]
+ *
+ */
+
+int findMin(vector<int> &num) {
+
+    int low=0, high=num.size()-1;
+
+    while(high-low>1){
+        //skip the same element, this would cause the O(n) run-time complexity. 
+        while (high - low > 1 && num[low] == num[high]){
+            low++;
+        }
+        //binary search
+        int mid = low + (high-low)/2;
+        //Notes: checking the equal situation
+        if (num[low] <= num[mid] && num[mid] <= num[high]){
+            return num[low] < num[mid] ? num[low] : num[mid];
+        }
+        //move the high pointer to the middle, if sub-array from low to mid is rotated.
+        if (num[low] > num [mid]){
+            high = mid;
+            continue;
+        }
+        // move the low pointer to the middle, if sub-array from mid to high is rotated.
+        if (num[mid] > num[high]){
+            low = mid;
+            continue;
+        }
+    }
+    
+    if (high == low) return num[low];
+    return num[low] < num[high] ? num[low] : num[high];
+
+}
+
+
+void rotate_array(int a[], int n, int pos){
+    int i, from=0;
+    pos = pos % n;
+    if (n<=0) return;
+
+    int tmp = a[0];
+
+    for(int i=0, step=0; step<n && i<pos; step++){
+        int to;
+        if (from-pos < 0) {
+            to = n-pos+from; 
+        }else{
+            to = from-pos;
+        }
+        int t ;
+        t = a[to];
+        a[to] = tmp; 
+        tmp = t;
+        from = to;
+        if ( to == i ){
+            i++;
+            from++;
+            tmp = a[from];
+        }
+    }
+
+}
+
+void printArray(int A[], int n) {
+    printf("{");
+    for(int i=0; i<n; i++) {
+        printf("%d, ", A[i]);
+    }
+    printf("}\n");
+}
+
+int main(int argc, char** argv)
+{
+
+    int cnt=20;
+
+    if (argc>1) {
+        cnt = atoi(argv[1]);
+    }
+
+    srand(time(NULL)); 
+
+    int expectedMin, actualMin;
+    int *a = new int[cnt];
+    for(int n=0; n<=cnt; n++) {
+        printf("--------------------------------------\n");
+        //generate the array with random elements
+        for(int i=0; i<cnt; i++){
+            a[i]=rand()%cnt;
+        }
+        //sort the array
+        sort(a, a+cnt); 
+        expectedMin = a[0];
+        //printArray(a, cnt);
+        int rotate_pos = random() % cnt;
+        //rotate_pos=2;
+        printf("rotate=%d\n", rotate_pos);
+        rotate_array(a, cnt, rotate_pos);
+        printArray(a, cnt);
+
+        vector<int> num(a, a+cnt);
+        actualMin = findMin(num);
+        cout << "findMin = " << actualMin << "   " << (expectedMin==actualMin ? "passed" : "failed") << endl;
+
+    }
+    delete[] a;
+
+    return 0;
+}
diff --git a/src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.cpp b/src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.cpp
@@ -93,12 +93,14 @@ int main(int argc, char** argv)
 
     srand(time(NULL)); 
 
+    int expectedMin, actualMin;
     int *a = new int[cnt];
     for(int n=0; n<=cnt; n++) {
         printf("--------------------------------------\n");
         for(int i=0; i<cnt; i++){
             a[i]=i;
         }
+        expectedMin = a[0];
         //printArray(a, cnt);
         int rotate_pos = random() % cnt;
         //rotate_pos=2;
@@ -107,7 +109,8 @@ int main(int argc, char** argv)
         printArray(a, cnt);
 
         vector<int> num(a, a+cnt);
-        cout << "findMin = " << findMin(num) << endl;
+        actualMin = findMin(num);
+        cout << "findMin = " << actualMin << "   " << (expectedMin==actualMin ? "passed" : "failed") << endl;
 
     }
     delete[] a;
