1 /**

2 * Created by areful on 2019/11/133 */

4 public classCalcStringNumber {5 private static final String REG_EXP_NUMBER = "0|(-?[1-9]+[0-9]*)";6 private static final String REG_EXP_NON_NEGATIVE_NUMBER = "0|([1-9]+[0-9]*)";7

8 /**

9 * 帶符號相加10 */

11 private staticString add(String s1, String s2) {12 assert s1.matches(REG_EXP_NUMBER) &&s2.matches(REG_EXP_NUMBER);13

14 boolean isPos1 = s1.charAt(0) != '-';15 boolean isPos2 = s2.charAt(0) != '-';16

17 if (isPos1 &&isPos2) {18 //都為非負數，直接無符號相加

19 returnaddPositive(s1, s2);20 } else if (!isPos1 && !isPos2) {21 //都為負數，無符號相加再取反

22 return '-' + addPositive(s1.substring(1), s2.substring(1));23 } else if(isPos1) {24 //1正，2負，比較字符串長度

25 if (s1.length() > s2.substring(1).length()) {26 //1比2長，正號

27 return subPositive(s1, s2.substring(1));28 } else if (s1.length() < s2.substring(1).length()) {29 //1比2短，負號

30 return '-' + subPositive(s1, s2.substring(1));31 } else{32 //長度相同，去掉符號比較字符串，根據比較結果做絕對值加減，并賦相應符號

33 int r = s1.compareTo(s2.substring(1));34 if (r > 0) return subPositive(s1, s2.substring(1));35 else if (r == 0) return "0";36 else return '-' + subPositive(s2.substring(1), s1);37 }38 } else{39 //1負，2正，比較字符串長度

40 if (s1.substring(1).length() >s2.length()) {41 //1比2長，負號

42 return '-' + subPositive(s1.substring(1), s2);43 } else if (s1.substring(1).length()

45 return subPositive(s2, s1.substring(1));46 } else{47 //長度相同，去掉符號比較字符串，根據比較結果做絕對值加減，并賦相應符號

48 int r = s1.substring(1).compareTo(s2);49 if (r > 0) return '-' + subPositive(s1.substring(1), s2);50 else if (r == 0) return "0";51 else return subPositive(s2, s1.substring(1));52 }53 }54 }55

56 /**

57 * 帶符號相減58 */

59 private staticString sub(String s1, String s2) {60 assert s1.matches(REG_EXP_NUMBER) &&s2.matches(REG_EXP_NUMBER);61

62 boolean isPos1 = s1.charAt(0) != '-';63 boolean isPos2 = s2.charAt(0) != '-';64

65 if (isPos1 && !isPos2) {66 //1正，2負，去掉負號，做正整數相加

67 return addPositive(s1, s2.substring(1));68 } else if (!isPos1 &&isPos2) {69 //1負，2正，絕對值相加再取負號

70 return '-' + addPositive(s1.substring(1), s2);71 } else if(isPos1) {72 //均為正，比較字符串長度

73 if (s1.length() >s2.length()) {74 //1比2長，正號

75 returnsubPositive(s1, s2);76 } else if (s1.length()

78 return '-' +subPositive(s2, s1);79 } else{80 //長度相同，比較字符串，根據比較結果做絕對值加減，并賦相應符號

81 int r =s1.compareTo(s2);82 if (r > 0) returnsubPositive(s1, s2);83 else if (r == 0) return "0";84 else return '-' +subPositive(s2, s1);85 }86 } else{87 //均為負，比較字符串長度

88 if (s1.length() >s2.length()) {89 //1比2長，負號

90 return '-' + subPositive(s1.substring(1), s2.substring(1));91 } else if (s1.length()

93 return subPositive(s2.substring(1), s1.substring(1));94 } else{95 //長度相同，比較字符串，根據比較結果做絕對值加減，并賦相應符號

96 int r =s1.compareTo(s2);97 if (r > 0) return '-' + subPositive(s1.substring(1), s2.substring(1));98 else if (r == 0) return "0";99 else return subPositive(s1.substring(1), s2.substring(1));100 }101 }102 }103

104 /**

105 * 無符號相加106 */

107 private staticString addPositive(String s1, String s2) {108 assert s1.matches(REG_EXP_NON_NEGATIVE_NUMBER) &&s2.matches(REG_EXP_NON_NEGATIVE_NUMBER);109

110 int len1 =s1.length();111 int len2 =s2.length();112 int len =Math.max(len1, len2);113

114 //暫存計算結果

115 int[] result = new int[len];116 //進位符號，為1表示有進位

117 int carry = 0;118 for (int i = 0; i < len; i++) {119 int a1 = i < len1 ? s1.charAt(len1 - 1 - i) - '0' : 0;120 int a2 = i < len2 ? s2.charAt(len2 - 1 - i) - '0' : 0;121 //帶進位相加

122 int a = a1 + a2 +carry;123 result[len - 1 - i] = a % 10;124 //判斷當前計算是否產生進位

125 carry = a > 9 ? 1 : 0;126 }127

128 StringBuilder sb = newStringBuilder();129 //有進位則頭部加1

130 if (carry == 1) sb.append('1');131 for (int i = 0; i < len; i++) sb.append(result[i]);132 returntrimZero(sb.toString());133 }134

135 /**

136 * 無符號相減137 */

138 private staticString subPositive(String s1, String s2) {139 assert s1.matches(REG_EXP_NON_NEGATIVE_NUMBER) &&s2.matches(REG_EXP_NON_NEGATIVE_NUMBER);140 if (s1.equals(s2)) return "0";141

142 int len1 =s1.length();143 int len2 =s2.length();144 int len =Math.max(len1, len2);145

146 //暫存計算結果

147 int[] result = new int[len];148 int carry = 0;149 for (int i = 0; i < len; i++) {150 int a1 = i < len1 ? s1.charAt(len1 - 1 - i) - '0' : 0;151 int a2 = i < len2 ? s2.charAt(len2 - 1 - i) - '0' : 0;152 //判斷低一位計算是否產生借位，如有借位則減1

153 if (carry == 1) a1--;154 if (a1 >=a2) {155 //不需要借位，直接相減

156 carry = 0;157 result[len - 1 - i] = a1 -a2;158 } else{159 //需要借位，置借位標識并相減

160 carry = 1;161 result[len - 1 - i] = a1 + 10 -a2;162 }163 }164

165 StringBuilder sb = newStringBuilder();166 for (int i = 0; i < len; i++) sb.append(result[i]);167 returntrimZero(sb.toString());168 }169

170 /**

171 * 移除0開頭的數字字符172 */

173 private staticString trimZero(String text) {174 StringBuilder sb = newStringBuilder();175 boolean needIgnore = true;176 for (charc : text.toCharArray()) {177 if (needIgnore && c == '0') continue;178 needIgnore = false;179 sb.append(c);180 }181 if (sb.length() == 0) sb.append('0');182 returnsb.toString();183 }184

185 public static voidmain(String[] args) {186 assert "0".equals(add("0", "0"));187 assert "-24".equals(add("-15", "-9"));188 assert "-6".equals(add("-15", "9"));189 assert "6".equals(add("15", "-9"));190 assert "24".equals(add("15", "9"));191 assert "2468".equals(add("1234", "1234"));192 assert "10470".equals(add("5235", "5235"));193 assert "0".equals(add("-1234", "1234"));194 assert "0".equals(add("1234", "-1234"));195 assert "-1".equals(add("1234", "-1235"));196 assert "1".equals(add("-1234", "1235"));197 assert "6".equals(add("15", "-9"));198 assert "-6".equals(add("-15", "9"));199 assert "24700000000000000000000000000000000000000000000000".equals(200 add("12350000000000000000000000000000000000000000000000", "12350000000000000000000000000000000000000000000000"));201

202 assert "0".equals(sub("0", "0"));203 assert "6".equals(sub("-9", "-15"));204 assert "-24".equals(sub("-9", "15"));205 assert "24".equals(sub("9", "-15"));206 assert "-6".equals(sub("9", "15"));207 assert "6".equals(sub("15", "9"));208 assert "-6".equals(sub("-15", "-9"));209 assert "-24".equals(sub("-15", "9"));210 assert "24".equals(sub("15", "-9"));211 assert "6".equals(sub("15", "9"));212 assert "-2469".equals(sub("-1234", "1235"));213 assert "-1".equals(sub("1234", "1235"));214 assert "0".equals(sub("1234", "1234"));215 assert "0".equals(sub("-1234", "-1234"));216 assert "-1234".equals(sub("0", "1234"));217 assert "1234".equals(sub("0", "-1234"));218 assert "1234".equals(sub("1234", "0"));219 assert "24700000000000000000000000000000000000000000000000".equals(220 sub("12350000000000000000000000000000000000000000000000", "-12350000000000000000000000000000000000000000000000"));221 }222 }

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