二分的模板
class Solution {
public int searchInsert(int[] nums, int target) {
int l = 0,r = nums.length-1;
while (l<=r){
int mid = (l+r)/2;
if (nums[mid] == target) return mid;
else if (nums[mid] > target) r = mid-1;
else l = mid+1;
}
return l;
}
}