In the C++ STL, the vector size() function return size_t, which is unsigned int, not int. So imagine this, define an empty vector<int> v, and v.size() should be 0, and you have a for loop, and has an end condition is v.size() - 1, which is 4294967295 actually, not -1. This might cause problem when i = 0, which can enter the for loop, but actually was supposed not entering it.In the C++ STL, the vector size() function
