hdu 3183（贪心）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=3183

思路：比较前后两个相邻的字符，如果前面一个字符大于后面一个字符，就把它去掉。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
#include <vector>
#define REP(i, a, b) for (int i = (a); i < (b); ++i)
#define FOR(i, a, b) for (int i = (a); i <= (b): ++i)
using namespace std;

const int MAX_N = (1000 + 100);
int N, M, len;
char str[MAX_N], ans[MAX_N];

int main()
{
	while (cin >> str >> M) {
		N = strlen(str), len = 0;
		REP(i, 0, N - 1) {
			if (str[i] > str[i + 1] && M) {
				--M;
				while (len - 1 >= 0 && ans[len - 1] > str[i + 1] && M) {
					--len, --M;
				}
			}
			else
				ans[len++] = str[i];
		}
		ans[len++] = str[N - 1];
		string tmp = "";
		REP(i, 0, len - M) tmp += ans[i];
		int p = 0;
		N = (int)tmp.size(), len = 0;
		while (p < N && tmp[p] == '0')++p;
		while (p < N) ans[len++] = tmp[p], ++p;
		ans[len] = 0;
		if (strlen(ans) == 0) {
			cout << 0 << endl;
		}
		else
			cout << ans << endl;
	}
	return 0;
}