[Swift]LeetCode1237. 找出给定方程的正整数解 | Find Positive Integer Solution for a Given Equation
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Given a function f(x, y) and a value z, return all positive integer pairs x and y where f(x,y) == z.
The function is constantly increasing, i.e.:
f(x, y) < f(x + 1, y)
f(x, y) < f(x, y + 1)
The function interface is defined like this:
interface CustomFunction {
public:
// Returns positive integer f(x, y) for any given positive integer x and y.
int f(int x, int y);
};
For custom testing purposes you're given an integer function_id and a target z as input, where function_id represent one function from an secret internal list, on the examples you'll know only two functions from the list.
You may return the solutions in any order.
Example 1:
Input: function_id = 1, z = 5
Output: [[1,4],[2,3],[3,2],[4,1]]
Explanation: function_id = 1 means that f(x, y) = x + y
Example 2:
Input: function_id = 2, z = 5
Output: [[1,5],[5,1]]
Explanation: function_id = 2 means that f(x, y) = x * y
Constraints:
1 <= function_id <= 9
1 <= z <= 100
It's guaranteed that the solutions of f(x, y) == z will be on the range 1 <= x, y <= 1000
It's also guaranteed that f(x, y) will fit in 32 bit signed integer if 1 <= x, y <= 1000
给出一个函数 f(x, y) 和一个目标结果 z，请你计算方程 f(x,y) == z 所有可能的正整数 数对 x 和 y。
给定函数是严格单调的，也就是说：
f(x, y) < f(x + 1, y)
f(x, y) < f(x, y + 1)
函数接口定义如下：
interface CustomFunction {
public:
// Returns positive integer f(x, y) for any given positive integer x and y.
int f(int x, int y);
};
如果你想自定义测试，你可以输入整数 function_id 和一个目标结果 z 作为输入，其中 function_id 表示一个隐藏函数列表中的一个函数编号，题目只会告诉你列表中的 2 个函数。
你可以将满足条件的 结果数对 按任意顺序返回。
示例 1：
输入：function_id = 1, z = 5
输出：[[1,4],[2,3],[3,2],[4,1]]
解释：function_id = 1 表示 f(x, y) = x + y
示例 2：
输入：function_id = 2, z = 5
输出：[[1,5],[5,1]]
解释：function_id = 2 表示 f(x, y) = x * y
提示：
1 <= function_id <= 9
1 <= z <= 100
题目保证 f(x, y) == z 的解处于 1 <= x, y <= 1000 的范围内。
在 1 <= x, y <= 1000 的前提下，题目保证 f(x, y) 是一个 32 位有符号整数。
