计算机中数据定义的长度是有限的，比如31位，或者63位，外加一位符号位。
1 *&---------------------------------------------------------------------* 2 *& Report ZCHENH048 3 *& 4 *&---------------------------------------------------------------------* 5 *& 6 *& 7 *&---------------------------------------------------------------------* 8 9 REPORT zchenh048. 10 *算法参考思想：https://blog.csdn.net/u010983881/article/details/77503519 11 DATA:num1 TYPE string, 12 num2 TYPE string, 13 result TYPE string. 14 num1 = 123456789. 15 num2 = 123456789. 16 CONDENSE:num1,num2. 17 PERFORM frm_big_mult USING num1 num2 CHANGING result. 18 WRITE:num1,'x',num2,'=',result. 19 *&---------------------------------------------------------------------* 20 *& Form FRM_BIG_MULT 21 *&---------------------------------------------------------------------* 22 * text 23 *----------------------------------------------------------------------* 24 * --> p1 text 25 * <-- p2 text 26 *----------------------------------------------------------------------* 27 FORM frm_big_mult USING value(n1) 28 value(n2) 29 CHANGING res. 30 DATA:lv_len1 TYPE i, 31 lv_len2 TYPE i, 32 halfn TYPE i, 33 mid TYPE i. 34 35 DATA:a TYPE string, 36 b TYPE string, 37 c TYPE string, 38 d TYPE string, 39 x TYPE string, 40 y TYPE string. 41 DATA:z0 TYPE string, 42 z1 TYPE string, 43 z2 TYPE string. 44 45 *递归终止条件 46 IF n1 < 10 OR n2 < 10. 47 res = n1 * n2. 48 ELSE. 49 * 计算拆分长度 50 CLEAR:lv_len1,lv_len2,halfn. 51 CONDENSE: n1,n2. 52 lv_len1 = strlen( n1 ). 53 lv_len2 = strlen( n2 ). 54 55 IF lv_len1 > lv_len2. 56 halfn = floor( lv_len1 / 2 ). " 向下取整 57 ELSE. 58 halfn = floor( lv_len2 / 2 ). 59 ENDIF. 60 * WRITE:/,'HALFN--->',halfn,'lv_len1--->',lv_len1,'lv_len2--->',lv_len2. 61 mid = lv_len1 - halfn. 62 a = n1+0(mid). 63 b = n1+mid(halfn). 64 65 mid = lv_len2 - halfn. 66 c = n2+0(mid). 67 d = n2+mid(halfn). 68 69 x = a + b. 70 y = c + d. 71 72 * WRITE:/,'a-->',a,'b-->',b,'c-->',c,'d-->',d,'x-->',x,'y-->',y. 73 * 计算z2, z0, z1, 此处的乘法使用递归 74 PERFORM frm_big_mult USING a c CHANGING z2. 75 PERFORM frm_big_mult USING b d CHANGING z0. 76 PERFORM frm_big_mult USING x y CHANGING z1. 77 z1 = z1 - z0 - z2. 78 * WRITE:/,'z0-->',z0,'z1-->',z1,'z2-->',z2. 79 PERFORM frm_math_n USING 10 2 halfn z2 CHANGING a. " 求N次方 80 PERFORM frm_math_n USING 10 1 halfn z1 CHANGING b. " 求N次方 81 res = a + b + z0 . 82 ENDIF. 83 ENDFORM. " FRM_BIG_MULT 84 *&---------------------------------------------------------------------* 85 *& Form FRM_MATH_N 86 *&---------------------------------------------------------------------* 87 * text 88 *----------------------------------------------------------------------* 89 * --> p1 text 90 * <-- p2 text 91 *----------------------------------------------------------------------* 92 FORM frm_math_n USING a1 b1 c1 d1 CHANGING e1 TYPE string. 93 DATA: res TYPE n LENGTH 30 . 94 res = a1 ** ( b1 * c1 ). 95 e1 = res * d1. 96 ENDFORM. " FRM_MATH_N 97 98 99 * JAVA版 100 *public class HelloWorld { 101 * public static void main(String []args) { 102 * long num1 = 1234567899; 103 * long num2 = 1234567899; 104 * System.out.println("大数相乘："+num1+" X "+num2+" = "+ karatsuba(num1,num2)); 105 * } 106 * public static long karatsuba(long num1, long num2){ 107 * //递归终止条件 108 * if(num1 < 10 || num2< 10) return num1 * num2; 109 * 110 * // 计算拆分长度 111 * int size1 = String.valueOf(num1).length(); 112 * int size2 = String.valueOf(num2).length(); 113 * int halfN = Math.max(size1, size2) / 2; 114 * 115 * /* 拆分为a, b, c, d */ 116 * long a = Long.valueOf(String.valueOf(num1).substring(0, size1 - halfN)); 117 * long b = Long.valueOf(String.valueOf(num1).substring(size1 - halfN)); 118 * long c = Long.valueOf(String.valueOf(num2).substring(0, size2 - halfN)); 119 * long d = Long.valueOf(String.valueOf(num2).substring(size2 - halfN)); 120 * 121 * // 计算z2, z0, z1, 此处的乘法使用递归 122 * long z2 = karatsuba(a, c); 123 * long z0 = karatsuba(b, d); 124 * long z1 = karatsuba((a + b), (c + d)) - z0 - z2; 125 * 126 * return (long)(z2 * Math.pow(10, (2*halfN)) + z1 * Math.pow(10, halfN) + z0); 127 *} 128 *}
运行结果：123456789 x 123456789 = 15241578750190521.0