Binary search.
public class Solution {
public int searchInsert(int[] nums, int target) {
int l = 0;
int r = nums.length;
while (l < r) {
int mid = (l + r) / 2;
if (nums[mid] == target) return mid;
else if (nums[mid] > target) r = mid;
else l = mid + 1;
}
return l;
}
}