delete k number to get the smallest int

Given a number, can you remove k digits from the number so that the new 
formatted number is smallest possible.

input: n = 1432219, k = 3
output: 1219

思想：贪心算法，查找规律

代码：

1. #include <iostream>
2. #include <string>
3. using namespace std;
4. string deleteKNumber(string &str,int k) {
5. string::iterator start;
6. bool flag = false;
7. for(int i=k;i>0;i--) {
8. flag = false;
9. for(start = str.begin();start<str.end()-1;++start) {
10. if(*start > *(start+1)) {
11. str.erase(start);
12. flag = 1;
13. break;
14. }
15. }
16. if(!flag) {
17. str.erase(str.end()-i,str.end());
18. break;
19. }
20. }
21. return str;
22. }
23. int main() {
24. string data="12469823859";
25. cout<<deleteKNumber(data,2)<<endl;
26. return 0;
27. }