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

题目传送门

 /*
     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 + ;
 const int INF = 0x3f3f3f3f;
 const int MOD = 1e9 + ;
 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) == ) {
         for (int i=; i<=n; ++i)    {
             scanf ("%s", s[i] + );
         }
         int ans = ;    memset (ok, false, sizeof (ok));
         bool flag = true;
         for (int j=; j<=m; ++j)    {
             flag = true;
             for (int i=; i<=n; ++i)    {
                 if (ok[i][i-]) continue;
                 if (s[i][j] < s[i-][j])    {
                     ans++;  flag = false;   break;
                 }
             }
             if (flag)   {
                 for (int k=; k<=n; ++k)    {
                     if (s[k][j] > s[k-][j])    ok[k][k-] = true;
                 }
             }
         }
         printf ("%d\n", ans);
     }

     return ;
 }