高精度模板（转载）

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高精度计算模板
注意：减法、除法要用到compare函数

乘法需要加法的部分，加法需要减法部分

//开头

#include <iostream>#include <string>using namespace std;int compare(string str1, string str2){     if(str1.size() > str2.size())        return 1;    else if(str1.size() < str2.size())        return -1;    else        return str1.compare(str2);}int main(){    char ch;    string s1, s2, res;    while(cin >> ch) {        cin >> s1>> s2;        switch(ch) {        case '+': res = ADD_INT(s1, s2); break; //高精度加法        case '-': res = MINUS_INT(s1, s2); break; //高精度减法        case '*': res = MULTIPLY_INT(s1, s2); break; //高精度乘法        case '/': res = DIV_INT(s1, s2); break; //高精度除法,返回商        case 'm': res = MOD_INT(s1, s2); break; //高精度除法,返回余数        default : break;}    cout << res<< endl;}    return(0);}

加法- -

//高精度加法string ADD_INT(string str1, string str2){    string MINUS_INT(string str1, string str2);    int sign = 1;     string str;    if(str1[0] == '-') {        if(str2[0] == '-') {            sign = -1;            str = ADD_INT(str1.erase(0, 1), str2.erase(0, 1));         }else {             str = MINUS_INT(str2, str1.erase(0, 1));         }    }else {        if(str2[0] == '-')            str = MINUS_INT(str1, str2.erase(0, 1));        else {            string::size_type l1, l2;            int i;            l1 = str1.size(); l2 = str2.size();            if(l1 < l2) {                for(i = 1; i <= (int)(l2 - l1); i++)                    str1 = "0" + str1;            }else {                for(i = 1; i <= (int)(l1 - l2); i++)                    str2 = "0" + str2;            }            int int1 = 0, int2 = 0;             for(i = str1.size() - 1; i >= 0; i--) {                int1 = (int(str1[i]) - 48 + int(str2[i]) - 48 + int2) %10;                 int2 = (int(str1[i]) - 48 + int(str2[i]) - 48 +int2) / 10;                str = char(int1 + 48) + str;            }            if(int2 != 0) str = char(int2 + 48) + str;        }    }    //运算后处理符号位    if((sign == -1) && (str[0] !='0'))        str = "-" + str;    return str;}

减法

//高精度减法string MINUS_INT(string str1, string str2){    string MULTIPLY_INT(string str1, string str2);    int i,sign = 1;    string str;    if(str2[0] == '-')        str = ADD_INT(str1, str2.erase(0, 1));    else {        int res = compare(str1, str2);        if(res == 0) return "0";        if(res < 0) {            sign = -1;            string temp = str1;            str1 = str2;            str2 = temp;}        string::size_type tempint;        tempint = str1.size() - str2.size();        for(int i = str2.size() - 1; i >= 0; i--) {            if(str1[i + tempint] < str2[i]) {                str1[i + tempint - 1] = char(int(str1[i + tempint - 1]) - 1);                str = char(str1[i + tempint] - str2[i] + 58) + str;}            else                str = char(str1[i + tempint] - str2[i] + 48) + str;}        for(i = tempint - 1; i >= 0; i--)            str = str1[i] + str;}    //去除结果中多余的前导0    str.erase(0, str.find_first_not_of('0'));    if(str.empty()) str = "0";    if((sign == -1) && (str[0] !='0'))        str = "-" + str;    return str;}

乘法

//高精度乘法string MULTIPLY_INT(string str1, string str2){    int sign = 1;     string str;    if(str1[0] == '-') {        sign *= -1;        str1 = str1.erase(0, 1);}    if(str2[0] == '-') {        sign *= -1;        str2 = str2.erase(0, 1);}    int i, j;    string::size_type l1, l2;    l1 = str1.size(); l2 = str2.size();    for(i = l2 - 1; i >= 0; i --) {    //实现手工乘法        string tempstr;        int int1 = 0, int2 = 0, int3 = int(str2[i]) - 48;        if(int3 != 0) {            for(j = 1; j <= (int)(l2 - 1 - i); j++)                 tempstr = "0" + tempstr;            for(j = l1 - 1; j >= 0; j--) {                int1 = (int3 * (int(str1[j]) - 48) + int2) % 10;                int2 = (int3 * (int(str1[j]) - 48) + int2) / 10;                tempstr = char(int1 + 48) + tempstr;}            if(int2 != 0) tempstr = char(int2 + 48) + tempstr;}        str = ADD_INT(str, tempstr);}    //去除结果中的前导0    str.erase(0, str.find_first_not_of('0'));    if(str.empty()) str = "0";    if((sign == -1) && (str[0] !='0'))        str = "-" + str;    return str;}

除法

//高精度除法string DIVIDE_INT(string str1, string str2, int flag){    //flag = 1时,返回商; flag = 0时,返回余数    string quotient, residue;     int sign1 = 1, sign2 = 1, i;    if(str2 == "0") {                                 //判断除数是否为0        quotient = "ERROR!";        residue = "ERROR!";        if(flag == 1) return quotient;        else return residue;}    if(str1 == "0") {                                 //判断被除数是否为0        quotient = "0";        residue = "0";}    if(str1[0] == '-') {        str1 = str1.erase(0, 1);        sign1 *= -1;        sign2 = -1;}    if(str2[0] == '-') {        str2 = str2.erase(0, 1);        sign1 *= -1;}    int res = compare(str1, str2);    if(res < 0) {        quotient = "0";        residue = str1;}else if(res == 0) {        quotient = "1";        residue = "0";}else {        string::size_type l1, l2;        l1 = str1.size(); l2 = str2.size();        string tempstr;        tempstr.append(str1, 0, l2 - 1);        //模拟手工除法        for(i = l2 - 1; i < l1; i++) {            tempstr = tempstr + str1[i];            for(char ch = '9'; ch >= '0'; ch --) {                 string str;                str = str + ch;                if(compare(MULTIPLY_INT(str2, str), tempstr) <= 0){                    quotient = quotient + ch;                    tempstr = MINUS_INT(tempstr, MULTIPLY_INT(str2, str));                    break;}}}        residue = tempstr;}    //去除结果中的前导0    quotient.erase(0, quotient.find_first_not_of('0'));    if(quotient.empty()) quotient = "0";    if((sign1 == -1) && (quotient[0] !='0'))        quotient = "-" + quotient;    if((sign2 == -1) && (residue[0] !='0'))        residue = "-" + residue;    if(flag == 1) return quotient;    else return residue;}//高精度除法,返回商string DIV_INT(string str1, string str2){    return DIVIDE_INT(str1, str2, 1);}//高精度除法,返回余数string MOD_INT(string str1, string str2){    return DIVIDE_INT(str1, str2, 0);}

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