Reference
Request
- Sorted Array
- Need
N(logN)
Templates
1. Standard Templates
class BinarySearch {
public int search(int[] nums, int target) {
int left = 0;
int right = nums.length - 1;
while (left <= right) {
int mid = left + ((right - left) >> 1);
if (nums[mid] == target) return mid;
else if (nums[mid] > target) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return -1;
}
}
2. Binary Search Left Boundary
class Solution {
public int search(int[] nums, int target) {
int left = 0;
int right = nums.length - 1;
while (left < right) {
int mid = left + (right - left) / 2;
if (nums[mid] < target) {
left = mid + 1;
} else {
right = mid;
}
}
return nums[left] == target ? left : -1;
}
}
3. Binary Search Right Boundary
class Solution {
public int search(int[] nums, int target) {
int left = 0;
int right = nums.length - 1;
while (left < right) {
int mid = left + ((right - left) >> 1) + 1;
if (nums[mid] > target) {
right = mid - 1;
} else {
left = mid;
}
}
return nums[right] == target ? right : -1;
}
}
Conclusion
| type |
while |
left update |
right update |
mid |
return |
| standard |
left <= right |
left = mid - 1 |
right = mid + 1 |
(left + right) / 2 |
-1 / mid |
| left boundary |
left < right |
left = mid - 1 |
right = mid |
(left + right) / 2 |
-1 / left |
| right boundary |
left < right |
left = mid |
right = mid - 1 |
(left + right) / 2 + 1 |
-1 / right |
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