34. Find First and Last Position of Element in Sorted Array

刷
June-21-2019

最早的时候被边界条件各种恶心。

YLNR大法，注意最后的边界。

    public int[] searchRange(int[] nums, int target) {
        if (nums == null || nums.length == 0 || nums[0] > target || nums[nums.length - 1] < target) {
            return new int[]{-1, -1};
        }
        
        int l = 0, r = nums.length - 1;
        while (l <= r) {
            int m = l + (r - l) / 2;
            
            if (nums[m] >= target) {
                r = m - 1;
            } else {
                l = m + 1;
            }
        }
        int[] result = new int[]{-1, -1};
        
        if (nums[l] != target) {
            return result;
        } else {
            result[0] = l;
        }
        
        l = 0;
        r = nums.length - 1;
        while (l <= r) {
            int m = l + (r - l) / 2;
            if (nums[m] <= target) {
                l = m + 1;
            } else {
                r = m - 1;
            }
        }
        result[1] = r;
        return result; 
    }