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algorithmzuoalgorithmzuo
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add class 05
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‎src/class05/Code01_BitMap1.java

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package class05;
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import java.util.HashSet;
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// 这个类的实现是错误的
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// 请问为什么？
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public class Code01_BitMap1 {
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public static class BitMap {
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private long[] bits;
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public BitMap(int max) {
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bits = new long[(max + 64) >> 6];
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}
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public void add(int num) {
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bits[num >> 6] |= (1 << (num & 63));
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}
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public void delete(int num) {
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bits[num >> 6] &= ~(1 << (num & 63));
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}
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public boolean contains(int num) {
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return (bits[num >> 6] & (1 << (num & 63))) != 0;
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}
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}
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public static void main(String[] args) {
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System.out.println("测试开始！");
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int max = 10000;
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BitMap bitMap = new BitMap(max);
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HashSet<Integer> set = new HashSet<>();
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int testTime = 10000000;
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for (int i = 0; i < testTime; i++) {
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int num = (int) (Math.random() * (max + 1));
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double decide = Math.random();
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if (decide < 0.333) {
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bitMap.add(num);
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set.add(num);
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} else if (decide < 0.666) {
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bitMap.delete(num);
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set.remove(num);
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} else {
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if (bitMap.contains(num) != set.contains(num)) {
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System.out.println("Oops!");
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break;
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}
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}
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}
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for (int num = 0; num <= max; num++) {
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if (bitMap.contains(num) != set.contains(num)) {
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System.out.println("Oops!");
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}
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}
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System.out.println("测试结束！");
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}
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}

‎src/class05/Code02_BitMap2.java

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package class05;
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import java.util.HashSet;
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public class Code02_BitMap2 {
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// 这个类的实现是正确的
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public static class BitMap {
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private long[] bits;
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public BitMap(int max) {
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bits = new long[(max + 64) >> 6];
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}
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public void add(int num) {
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bits[num >> 6] |= (1L << (num & 63));
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}
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public void delete(int num) {
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bits[num >> 6] &= ~(1L << (num & 63));
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}
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public boolean contains(int num) {
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return (bits[num >> 6] & (1L << (num & 63))) != 0;
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}
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}
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public static void main(String[] args) {
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System.out.println("测试开始！");
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int max = 10000;
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BitMap bitMap = new BitMap(max);
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HashSet<Integer> set = new HashSet<>();
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int testTime = 10000000;
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for (int i = 0; i < testTime; i++) {
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int num = (int) (Math.random() * (max + 1));
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double decide = Math.random();
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if (decide < 0.333) {
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bitMap.add(num);
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set.add(num);
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} else if (decide < 0.666) {
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bitMap.delete(num);
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set.remove(num);
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} else {
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if (bitMap.contains(num) != set.contains(num)) {
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System.out.println("Oops!");
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break;
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}
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}
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}
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for (int num = 0; num <= max; num++) {
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if (bitMap.contains(num) != set.contains(num)) {
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System.out.println("Oops!");
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}
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}
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System.out.println("测试结束！");
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}
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}

‎src/class05/Code03_BitAddMinusMultiDiv.java

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package class05;
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// 测试链接：https://leetcode.com/problems/divide-two-integers
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public class Code03_BitAddMinusMultiDiv {
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public static int add(int a, int b) {
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int sum = a;
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while (b != 0) {
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sum = a ^ b;
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b = (a & b) << 1;
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a = sum;
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}
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return sum;
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}
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public static int negNum(int n) {
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return add(~n, 1);
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}
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public static int minus(int a, int b) {
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return add(a, negNum(b));
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}
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public static int multi(int a, int b) {
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int res = 0;
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while (b != 0) {
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if ((b & 1) != 0) {
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res = add(res, a);
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}
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a <<= 1;
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b >>>= 1;
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}
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return res;
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}
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public static boolean isNeg(int n) {
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return n < 0;
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}
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public static int div(int a, int b) {
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int x = isNeg(a) ? negNum(a) : a;
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int y = isNeg(b) ? negNum(b) : b;
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int res = 0;
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for (int i = 31; i > negNum(1); i = minus(i, 1)) {
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if ((x >> i) >= y) {
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res |= (1 << i);
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x = minus(x, y << i);
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}
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}
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return isNeg(a) ^ isNeg(b) ? negNum(res) : res;
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}
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public static int divide(int dividend, int divisor) {
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if (divisor == Integer.MIN_VALUE) {
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return dividend == Integer.MIN_VALUE ? 1 : 0;
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}
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if (dividend == Integer.MIN_VALUE) {
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if (divisor == negNum(1)) {
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return Integer.MAX_VALUE;
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}
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int res = div(add(dividend, 1), divisor);
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return add(res, div(minus(dividend, multi(res, divisor)), divisor));
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}
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return div(dividend, divisor);
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}
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}

‎src/class05/Code04_GetMax.java

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package class05;
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public class Code04_GetMax {
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public static int flip(int n) {
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return n ^ 1;
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}
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public static int sign(int n) {
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return flip((n >> 31) & 1);
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}
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public static int getMax1(int a, int b) {
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int c = a - b;
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int scA = sign(c);
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int scB = flip(scA);
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return a * scA + b * scB;
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}
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public static int getMax2(int a, int b) {
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int c = a - b;
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int sa = sign(a);
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int sb = sign(b);
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int sc = sign(c);
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int difSab = sa ^ sb;
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int sameSab = flip(difSab);
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int returnA = difSab * sa + sameSab * sc;
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int returnB = flip(returnA);
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return a * returnA + b * returnB;
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}
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public static void main(String[] args) {
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int a = -16;
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int b = 1;
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System.out.println(getMax1(a, b));
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System.out.println(getMax2(a, b));
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a = 2147483647;
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b = -2147480000;
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System.out.println(getMax1(a, b)); // wrong answer because of overflow
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System.out.println(getMax2(a, b));
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}
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}

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