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26. Remove Duplicates from Sorted Array
Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length.
Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.
Example 1:
Given nums = [1,1,2], Your function should return length =2, with the first two elements of `nums` being1and2respectively. It doesn't matter what you leave beyond the returned length.
Example 2:
Given nums = [0,0,1,1,1,2,2,3,3,4], Your function should return length =5, with the first five elements of `nums` being modified to0,1,2,3, and4respectively. It doesn't matter what values are set beyond the returned length.
Clarification:
Confused why the returned value is an integer but your answer is an array?
Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.
Internally you can think of this:
// nums is passed in by reference. (i.e., without making a copy)
int len = removeDuplicates(nums);
// any modification to nums in your function would be known by the caller.
// using the length returned by your function, it prints the first len elements.
for (int i = 0; i < len; i++) {
print(nums[i]);
}
解题分析
把后面的数据向前拷贝。
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public static int removeDuplicates(int[] nums) {
if (Objects.isNull(nums) || nums.length == 0) {
return 0;
}
int i = 0;
for (int j = 1; j < nums.length; j++) {
if (nums[i] != nums[j]) {
i++;
nums[i] = nums[j];
}
}
return i + 1;
}
public static int removeDuplicates1(int[] nums) {
if (nums == null || nums.length == 0) {
return 0;
}
int result = nums.length;
if (nums.length == 1) {
return result;
}
int previousNum = nums[0];
int minuendIndex = 0;
for (int i = 1; i < nums.length; i++) {
if (previousNum == nums[i]) {
minuendIndex++;
result--;
} else {
previousNum = nums[i];
}
if (minuendIndex > 0) {
nums[i - minuendIndex] = nums[i];
}
}
return result;
}
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public static int removeDuplicates(int[] nums) {
if (nums == null || nums.length == 0) {
return 0;
}
int result = 0;
for (int i = 0; i < nums.length; i++) {
if (nums[result] != nums[i]) {
result++;
}
nums[result] = nums[i];
}
return result + 1;
}