题目:把一个数组最开始的若干个元素搬到数组的末尾,我们称之为数组的旋转。输入一个递增排序的数组的一个旋转,输出旋转数组的最小元素。例如,数组{3,4,5,1,2}为{1,2,3,4,5}的一个旋转,该数组的最小值为1。
思路:分为两种情况,如果第一个元素和最后一个元素不相等,则用二分法;如果第一个元素等于最后一个元素,则用顺序查找。
解决方案:
public class Question11 {
public static int min(int[] numbers, int length){
if (numbers == null || length < 0) try {
throw new Exception("Invalid parameters");
} catch (Exception e) {
e.printStackTrace();
}
int index1 = 0;
int index2 = length - 1;
int indexMid = index1;
while (numbers[index1] >= numbers[index2]){
if (index2-index1 == 1){
indexMid = index2;
break;
}
indexMid = (index1 + index2) / 2;
if (numbers[index1] == numbers[index2] && numbers[indexMid] == numbers[index1]){
return minInOrder(numbers, index1, index2);
}
if (numbers[indexMid] >= numbers[index1]){
index1 = indexMid;
}
if (numbers[indexMid] <= numbers[index2]){
index2 = indexMid;
}
}
return numbers[indexMid];
}
private static int minInOrder(int[] numbsers, int index1, int index2){
int result = numbsers[index1];
for (int i=index1 + 1; i<=index2; i++){
if (result > numbsers[i]){
result = numbsers[i];
}
}
return result;
}
public static void main(String[] args) {
int[] numbers = new int[]{3,4,5,1,2};
int[] numbers1 = new int[]{1,0,1,1,1,1};
System.out.println(min(numbers, numbers.length));
System.out.println(min(numbers1, numbers1.length));
}
}