string的find函数，返回下标，当不存在时返回string::npos，为无符号数最大值_loveprogram_1的专栏

#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>

using namespace std;

int main( void )
{
	string str("abc");

	string::size_type i = str.find( "d" );

	cout << "i=" << i << endl;
	cout << "string::npos=" << string::npos << endl;
	// 此时i = npos = 4294967295，无符号数最大值
	unsigned int j = 0xffffffff;
	cout << "j=" << j << endl;// j = i = npos;

	return 0;
}#include <iostream>
#include <sstrea