##Binary Search
####正常用法
- 需要sorted
- 一般不带duplicate,有duplicate就有变化
####log(n)
- k numbers ---> k/2 numbers
####Basic Model
int end = nums.length - 1;
int start = 0;
while (end > start+1) {
int mid = start + (end - start) / 2;
if (nums[mid] == target) {
end = mid;
} else if (nums[mid] > target) {
end = mid;
} else {
start = mid;
}
}
if (nums[end] == target) {
return end;
} else if(nums[start] == target) {
return start;
}