35 Search Insertion position

public class Solution {
    public int searchInsert(int[] nums, int target) {
        if(nums == null || nums.length == 0) {
            return 0;
        }
        int res = 0;
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] == target) {
                return i;
            }
            if (nums[i] < target) {
                continue;
            }
            if (nums[i] > target) {
                res = i;
                return res;
            }
        }
        res = nums.length;
        return res;
    }
}

以上是自己写的

参考九章答案：用二分

find the first position >= target

public class Solution {
    public int searchInsert(int[] nums, int target) {
        int start = 0;
        int end = nums.length -1;

        while (start + 1 < end) {
            int mid = start + (end - start)/2;
            if (nums[mid] == target) {
                return mid;
            } else if (nums[mid] < target) {
                start = mid;
            } else {
                end = mid;
            }
        }

        if (nums[start] >= target) {
            return start;
        } else if (nums[end] >= target) {
            return end;
        } else {
            return end+1;
        }
    }
}

find the last position <= target

public class Solution {
    public int searchInsert(int[] A, int target) {
        int start = 0;
        int end = A.length - 1;
        int mid;

        if (target < A[0]) {
            return 0;
        }
        // find the last number less than target
        while (start + 1 < end) {
            mid = start + (end - start) / 2;
            if (A[mid] == target) {
                return mid;
            } else if (A[mid] < target) {
                start = mid;
            } else {
                end = mid;
            }
        }

        if (A[end] == target) {
            return end;
        }
        if (A[end] < target) {
            return end + 1;
        }
        if (A[start] == target) {
            return start;
        }
        return start + 1;
    }
}