暴力+构造 Codeforces Round #283 (Div. 2) C. Removing Columns

 /*
题意：删除若干行，使得n行字符串成递增排序
暴力+构造：从前往后枚举列，当之前的顺序已经正确时，之后就不用考虑了，这样删列最小
*/
/************************************************
Author        :Running_Time
Created Time  :2015-8-3 10:49:53
File Name     :C.cpp
*************************************************/

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int MAXN = 1e2 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
char s[MAXN][MAXN];
int n, m;
bool ok[MAXN][MAXN];

int main(void)    {       //Codeforces Round #283 (Div. 2) C. Removing Columns
while (scanf ("%d%d", &n, &m) == 2) {
for (int i=1; i<=n; ++i)    {
scanf ("%s", s[i] + 1);
}
int ans = 0;    memset (ok, false, sizeof (ok));
bool flag = true;
for (int j=1; j<=m; ++j)    {
flag = true;
for (int i=2; i<=n; ++i)    {
if (ok[i][i-1]) continue;
if (s[i][j] < s[i-1][j])    {
ans++;  flag = false;   break;
}
}
if (flag)   {
for (int k=2; k<=n; ++k)    {
if (s[k][j] > s[k-1][j])    ok[k][k-1] = true;
}
}
}
printf ("%d\n", ans);
}

return 0;
}