[LeetCode] Largest Number
Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330. Note: The result may be very large, so you need to return a string instead of an integer.
思路：先对输入的数组进行排序，然后把拍过序的数组里的数字接起来。
下面的代码在处理 [ 5, 51] 时给出 551，在处理 [51, 5] 时，给出 515。下面的代码是无法通过测试的。
class Solution {
public:
string largestNumber(vector<int> &num) {
sort( num.begin(), num.end(), myfunc );
string result;
for(int i=0; i<num.size(); i++)
{
result = result + int2str(num[i]);
}
return result;
}
bool myfunc(int x, int y)
{
string x_str = int2str(x);
string y_str = int2str(y);
for(int i=0; i<min( x_str.size(), y_str.size()); i++)
{
if( x_str[i] < y_str[i] )
return false;
if( x_str[i] > y_str[i] )
return true;
}
return true;
}
string int2str(int x)
{
string str = "";
while(x)
{
// ( int + char ) gives an int. We need to cast int into a char.
// (char + string) gives a string.
str = (char)(x%10+'0')+ str;
x = x/10;
}
return str;
}
};
下面给出通过测试的正确的代码：
class Solution {
public:
string largestNumber(vector<int> &num) {
sort( num.begin(), num.end(), myfunc );
if (num[0]==0){return "0";} // when input is [0,0], output should be "0" instead of "00"
string result;
for(int i=0; i<num.size(); i++)
{
result = result + int2str(num[i]);
}
return result;
}
static bool myfunc(int x, int y)
{
string x_str = int2str(x);
string y_str = int2str(y);
string str1 = x_str + y_str;
string str2 = y_str + x_str;
return str1>str2;
}
static string int2str(int x)
{
if(x==0)
return "0";
string str = "";
while(x)
{
// ( int + char ) gives an int. We need to cast int into a char.
// (char + string) gives a string.
str = (char)(x%10+'0')+ str;
x = x/10;
}
return str;
}
};