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package class38;
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// 来自字节
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// 给定两个数a和b
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// 第1轮，把1选择给a或者b
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// 第2轮，把2选择给a或者b
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// ...
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// 第i轮，把i选择给a或者b
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// 想让a和b的值一样大，请问至少需要多少轮？
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public class Code01_FillGapMinStep {
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// 暴力方法
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// 不要让a、b过大！
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public static int minStep0(int a, int b) {
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if (a == b) {
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return 0;
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}
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int limit = 15;
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return process(a, b, 1, limit);
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}
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public static int process(int a, int b, int i, int n) {
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if (i > n) {
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return Integer.MAX_VALUE;
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}
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if (a + i == b || a == b + i) {
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return i;
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}
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return Math.min(process(a + i, b, i + 1, n), process(a, b + i, i + 1, n));
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}
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public static int minStep1(int a, int b) {
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if (a == b) {
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return 0;
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}
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int s = Math.abs(a - b);
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int num = 1;
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int sum = 0;
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for (; !(sum >= s && (sum - s) % 2 == 0); num++) {
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sum += num;
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}
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return num - 1;
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}
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public static int minStep2(int a, int b) {
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if (a == b) {
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return 0;
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}
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int s = Math.abs(a - b);
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// 找到sum >= s, 最小的i
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int begin = best(s << 1);
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for (; (begin * (begin + 1) / 2 - s) % 2 != 0;) {
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begin++;
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}
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return begin;
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}
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public static int best(int s2) {
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int L = 0;
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int R = 1;
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for (; R * (R + 1) < s2;) {
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L = R;
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R *= 2;
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}
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int ans = 0;
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while (L <= R) {
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int M = (L + R) / 2;
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if (M * (M + 1) >= s2) {
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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 ans;
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}
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public static void main(String[] args) {
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System.out.println("功能测试开始");
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for (int a = 1; a < 100; a++) {
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for (int b = 1; b < 100; b++) {
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int ans1 = minStep0(a, b);
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int ans2 = minStep1(a, b);
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int ans3 = minStep2(a, b);
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if (ans1 != ans2 || ans1 != ans3) {
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System.out.println("出错了！");
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System.out.println(a + " , " + b);
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break;
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}
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}
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}
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System.out.println("功能测试结束");
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int a = 19019;
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int b = 8439284;
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int ans2 = minStep1(a, b);
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int ans3 = minStep2(a, b);
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System.out.println(ans2);
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System.out.println(ans3);
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}
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}
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