Follow up for "Search in Rotated Sorted Array":
What if duplicates are allowed?
What if duplicates are allowed?
Would this affect the run-time complexity? How and why?
Write a function to determine if a given target is in the array.
假设原数组是{1,2,3,3,3,3,3},那么旋转之后有可能是{3,3,3,3,3,1,2},或者{3,1,2,3,3,3,3},这样的我们判断左边缘和中心的时候都是3,如果我们要寻找1或者2,我们并不知道应该跳向哪一半。解决的办法只能是对边缘移动一步,直到边缘和中间不在相等或者相遇,这就导致了会有不能切去一半的可能。所以最坏情况(比如全部都是一个元素,或者只有一个元素不同于其他元素,而他就在最后一个)就会出现每次移动一步,总共是n步,算法的时间复杂度变成O(n)。
public class Solution {
public boolean search(int[] nums, int target) {
if (nums == null || nums.length == 0) {
return false;
}
int left = 0;
int right = nums.length - 1;
while (left <= right) {
int mid = (left + right) / 2;
if (nums[mid] == target) {
return true;
}
if (nums[mid] > nums[left]) {
if (target >= nums[left] && target < nums[mid]) {
right = mid - 1;
} else {
left = mid + 1;
}
} else if (nums[mid] < nums[left]) {
if (target <= nums[right] && target > nums[mid]) {
left = mid + 1;
} else {
right = mid - 1;
}
} else {
left++;
}
}
return false;
}
}
public class Solution {
public boolean search(int[] A, int target) {
if (A.length == 0 || A == null){
return false;
}
int start = 0;
int end = A.length - 1;
while (start + 1 < end){
int mid = start + (end - start) / 2;
// if (A[mid] == target){
// return true;
// }
if (A[start] == A[mid]){//if start == mid 可能出现mid在第一区也可能第二区
start++;// 所以用start++ 来判断
} else if (A[mid] > A[start]){// case Mid1
if (target >= A[start] && target <= A[mid]){//
end = mid;
} else {
start = mid;
}
} else if (A[mid] < A[start]) { //case Mid2
if (A[start] > target && A[mid] < target){
start = mid;
} else {
end = mid;
}
} else {
end--;
}
}
if (A[start] == target){
return true;
} else if (A[end] == target){
return true;
} else {
return false;
}
}
}
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