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167. 两数之和 II 输入有序数组 Two-sum-ii-input-array-is-sorted 🌟🌟
168. Excel表列名称 Excel Sheet Column Title 🌟
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167. 两数之和 II 输入有序数组 Two-sum-ii-input-array-is-sorted
numberstargetnumbers[index1]numbers[index2]1 <= index1 < index2 <= numbers.length[index1, index2]index1index2你可以假设每个输入 只对应唯一的答案 ，而且你 不可以 重复使用相同的元素。
你所设计的解决方案必须只使用常量级的额外空间。
示例 1：
输入：numbers = [2,7,11,15], target = 9 输出：[1,2] 解释：2 与 7 之和等于目标数 9 。因此 index1 = 1, index2 = 2 。返回 [1, 2] 。
示例 2：
输入：numbers = [2,3,4], target = 6 输出：[1,3] 解释：2 与 4 之和等于目标数 6 。因此 index1 = 1, index2 = 3 。返回 [1, 3] 。
示例 3：
输入：numbers = [-1,0], target = -1 输出：[1,2] 解释：-1 与 0 之和等于目标数 -1 。因此 index1 = 1, index2 = 2 。返回 [1, 2] 。
提示：
2 <= numbers.length <= 3 * 10^4-1000 <= numbers[i] <= 1000numbers-1000 <= target <= 1000代码1： 双指针
package mainimport "fmt"func twoSum(numbers []int, target int) []int {i, j := 0, len(numbers)-1for i < j {sum := numbers[i] + numbers[j]if sum == target {return []int{i + 1, j + 1}} else if sum < target {i++} else {j--}}return []int{}
}func main() {numbers := []int{2, 7, 11, 15}target := 9fmt.Println(twoSum(numbers, target))numbers = []int{2, 3, 4}target = 6fmt.Println(twoSum(numbers, target))numbers = []int{-1, 0}target = -1fmt.Println(twoSum(numbers, target))
}
代码2： 二分查找
package mainimport "fmt"func binarySearch(numbers []int, target, left int) int {right := len(numbers) - 1for left <= right {mid := (left + right) / 2if numbers[mid] == target {return mid} else if numbers[mid] > target {right = mid - 1} else {left = mid + 1}}return -1
}func twoSum(numbers []int, target int) []int {for i, x := range numbers {j := binarySearch(numbers, target-x, i+1)if j != -1 {return []int{i + 1, j + 1}}}return []int{}
}func main() {numbers := []int{2, 7, 11, 15}target := 9fmt.Println(twoSum(numbers, target))numbers = []int{2, 3, 4}target = 6fmt.Println(twoSum(numbers, target))numbers = []int{-1, 0}target = -1fmt.Println(twoSum(numbers, target))
}
代码3： 哈希表
package mainimport "fmt"func twoSum(numbers []int, target int) []int {index := make(map[int]int)for i, x := range numbers {if j, ok := index[target-x]; ok {return []int{j + 1, i + 1}}index[x] = i}return []int{}
}func main() {numbers := []int{2, 7, 11, 15}target := 9fmt.Println(twoSum(numbers, target))numbers = []int{2, 3, 4}target = 6fmt.Println(twoSum(numbers, target))numbers = []int{-1, 0}target = -1fmt.Println(twoSum(numbers, target))
}
输出：
[1 2]
[1 3]
[1 2]
168. Excel表列名称 Excel Sheet Column Title
columnNumber例如：
A -> 1 B -> 2 C -> 3 ... Z -> 26 AA -> 27 AB -> 28 ...
示例 1：
输入：columnNumber = 1 输出："A"
示例 2：
输入：columnNumber = 28 输出："AB"
示例 3：
输入：columnNumber = 701 输出："ZY"
示例 4：
输入：columnNumber = 2147483647 输出："FXSHRXW"
提示：
1 <= columnNumber <= 2^31 - 1代码1： 递归
package mainimport "fmt"func convertToTitle(columnNumber int) string {if columnNumber <= 26 {return string('A' + columnNumber - 1)}mod := (columnNumber - 1) % 26return convertToTitle((columnNumber-1)/26) + string('A'+mod)
}func main() {fmt.Println(convertToTitle(1))fmt.Println(convertToTitle(28))fmt.Println(convertToTitle(701))fmt.Println(convertToTitle(2147483647))
}
代码2：迭代
package mainimport "fmt"func convertToTitle(columnNumber int) string {ans := ""for columnNumber > 0 {mod := (columnNumber - 1) % 26ans = string('A'+mod) + anscolumnNumber = (columnNumber - 1) / 26}return ans
}func main() {fmt.Println(convertToTitle(1))fmt.Println(convertToTitle(28))fmt.Println(convertToTitle(701))fmt.Println(convertToTitle(2147483647))
}
输出：
A
AB
ZY
FXSHRXW
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