Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.
Note:
- The length of both num1 and num2 is < 5100.
- Both num1 and num2 contains only digits 0-9.
- Both num1 and num2 does not contain any leading zero.
- You must not use any built-in BigInteger library or convert the inputs to integer directly.
不使用内置 Int 类库，完成字符串的相加。
实现
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public String (String num1, String num2) {
if(num1 == null || num1.length() == 0) {
return num2;
}
if(num2 == null || num2.length() == 0) {
return num1;
}
char[] chAry = num1.toCharArray();
Stack<Character> aSk = new Stack<>();
for(Character a: chAry) {
aSk.add(a);
}
char[] chBry = num2.toCharArray();
Stack<Character> bSk = new Stack<>();
for(Character b: chBry) {
bSk.add(b);
}
int aLen = num1.length();
int bLen = num2.length();
List<Integer> result = new ArrayList<>();
int temp = 0;
while (!aSk.isEmpty() || !bSk.isEmpty()) {
char a = '0';
if(!aSk.isEmpty()) {
a = aSk.pop();
}
char b = '0';
if(!bSk.isEmpty()) {
b = bSk.pop();
}
int res = a + b - 96 + temp;
if (res >= 10){
temp = 1;
res = res - 10;
} else {
temp = 0;
}
result.add(res);
}
StringBuilder build = new StringBuilder();
int size = result.size();
if (temp == 1){
build.append(1);
}
for (int i= size - 1 ; i >= 0 ; i--){
build.append(result.get(i));
}
return build.toString();
}
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讨论区其他答案
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public String (String num1, String num2) {
StringBuilder sb = new StringBuilder();
int carry = 0;
for(int i = num1.length() - 1, j = num2.length() - 1; i >= 0 || j >= 0 || carry == 1; i--, j--){
int x = i < 0 ? 0 : num1.charAt(i) - '0';
int y = j < 0 ? 0 : num2.charAt(j) - '0';
sb.append((x + y + carry) % 10);
carry = (x + y + carry) / 10;
}
return sb.reverse().toString();
}
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参考资料
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