代码实现：

二分法：

方法一：非递归，左闭右闭

int searchInsert(int *nums, int numsSize, int target) {
    int l = 0, r = numsSize - 1; // 左闭右闭
    int mid;
    while (l <= r) {
        mid = (l + r) / 2;
        if (nums[mid] == target) {
            return mid;
        }
        if (nums[mid] > target) {
            r = mid - 1;
        } else {
            l = mid + 1;
        }
    }
    return l; // return r + 1; 
}

方法二：非递归，左闭右开

int searchInsert(int *nums, int numsSize, int target) {
    int l = 0, r = numsSize; // 左闭右开
    int mid;
    while (l < r) {
        mid = (l + r) / 2;
        if (nums[mid] == target) {
            return mid;
        }
        if (nums[mid] > target) {
            r = mid;
        } else {
            l = mid + 1;
        }
    }
    return l; // return r
}

方法三：递归，左闭右开

// 左闭右开
int search(int *nums, int l, int r, int target) {
    if (l >= r) {
        return l; // return r;
    }
    int mid = (l + r) / 2;
    if (nums[mid] == target) {
        return mid;
    }
    if (nums[mid] > target) {
        r = mid;
    } else {
        l = mid + 1;
    }
    return search(nums, l, r, target);
}

int searchInsert(int *nums, int numsSize, int target) {
    return search(nums, 0, numsSize, target);
}