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32 lines
866 B
32 lines
866 B
package class_2023_01_1_week;
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// 一个正整数如果能被 a 或 b 整除，那么它是神奇的。
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// 给定三个整数 n , a , b ，返回第 n 个神奇的数字。
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// 因为答案可能很大，所以返回答案 对 10^9 + 7 取模 后的值。
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// 测试链接 : https://leetcode.cn/problems/nth-magical-number/
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public class Code02_NthMagicalNumber {
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public static int nthMagicalNumber(int n, int a, int b) {
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// 求a和b的最小公倍数
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long lcm = (long) a / gcd(a, b) * b;
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long ans = 0;
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// l = 0
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// r = (long) n * Math.min(a, b)
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for (long l = 0, r = (long) n * Math.min(a, b), m = 0; l <= r;) {
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m = (l + r) / 2;
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if (m / a + m / b - m / lcm >= n) {
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ans = m;
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r = m - 1;
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} else {
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l = m + 1;
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}
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}
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return (int) (ans % 1000000007);
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}
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public static int gcd(int a, int b) {
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return b == 0 ? a : gcd(b, a % b);
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}
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}
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