标签:NSInteger 运算 大数 str2 str1 NSString length 减法 muString2
标题 大数减法运算
/**
*大数减法运算
**/
-(NSString *)reductionActionString:(NSString *)str1 andString:(NSString *)str2{
NSMutableString *muString1 = [[NSMutableString alloc] init];
NSMutableString *muString2 = [[NSMutableString alloc] init];
//正负数判断
NSString *negative = @"";
//如果相加的两个数的长度不一样 则通过补0补成长度一样的
if (str1.length > str2.length) {
NSInteger count = str1.length - str2.length;
NSInteger i = 0;
while (i < count) {
//在指定下标 index 插入一个字符串
[muString2 insertString:@"0" atIndex:i];
i++;
}
[muString1 appendString:str1];
[muString2 appendString:str2];
}else if (str1.length < str2.length){
NSInteger count = str2.length - str1.length;
NSInteger i = 0;
while (i < count) {
//在指定下标 index 插入一个字符串
[muString2 insertString:@"0" atIndex:i];
i++;
}
[muString1 appendString:str2];
[muString2 appendString:str1];
negative = @"-";
}else{
//长度相等时,从首位到末尾逐步判断大小
NSInteger i = 0;
while (i < str1.length) {
//取出当前需要判断的数据
NSString *number1 = [str1 substringWithRange:NSMakeRange(i, 1)];
NSString *number2 = [str2 substringWithRange:NSMakeRange(i, 1)];
NSInteger sub1 = [number1 integerValue];
NSInteger sub2 = [number2 integerValue];
if(sub1 < sub2){
negative = @"-";
break;
}
i++;
}
if ([negative isEqualToString:@"-"]) {
[muString1 appendString:str2];
[muString2 appendString:str1];
}else{
[muString1 appendString:str1];
[muString2 appendString:str2];
}
}
NSMutableString *numberString = [[NSMutableString alloc] init];
if (muString1.length == muString2.length) {
NSInteger i = 0;
NSUInteger borrow = 0;
while (i < muString1.length) {
//取出当前需要计算的数据
NSString *str1 = [muString1 substringWithRange:NSMakeRange(muString1.length -1 -i, 1)];
NSString *str2 = [muString2 substringWithRange:NSMakeRange(muString2.length -1 -i, 1)];
NSInteger sub1 = [str1 integerValue];
NSInteger sub2 = [str2 integerValue];
//判断当前位数是否被借1
if (borrow == 1) {
sub1 = sub1 -1;
}
NSInteger number = 0;
if(sub1 < sub2){
//如果被减数大于减数,则向高位借一
number = sub1 + 10 - sub2;
borrow = 1;
}else{
number = sub1 - sub2;
borrow = 0;
}
[numberString insertString:[NSString stringWithFormat:@"%ld",(long)number] atIndex:0];
i++;
}
}
//去掉无效的0
NSInteger k = 0;
NSInteger numberLength = numberString.length;
while (k < numberLength -1) {
NSString *str1 = [numberString substringWithRange:NSMakeRange(0, 1)];
if ([str1 integerValue] == 0) {
//去掉无效的0
[numberString deleteCharactersInRange:NSMakeRange(0, 1)];
}else{
break;
}
k++;
}
return [NSString stringWithFormat:@"%@%@",negative,numberString];
}
标签:NSInteger,运算,大数,str2,str1,NSString,length,减法,muString2 来源: https://blog.csdn.net/qq_39242343/article/details/122875931
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