SRM 630 DIV2

SRM 630 DIV2

第一次TC，本来以为AK了，结果1000分还是被系统cha掉了，不过倒是也cha掉了房间其他人赚了不少

A：字符串长度才50，直接简单的模拟即可
B：结点个数才10，先做一边floyd，找出两两之间路径，然后暴力枚举选哪些点，判断可不可以，如果可以的话，记录下最大个数
C：一开始的做法是，构造出rank数组后，对于连续的一段，都放a，然后最后一个放b即可，以为这样构造出来的肯定是字典序最小的，结果被系统cha掉了。
正确做法：一开始先构造出sa数组，暴力枚举每个位置，非'a'的，只要减1，保证字典序小了，在去构造一下sa数组，判断一下两个后缀数组一不一样，如果所有位置都不一样，说明这个是字典序最小的

代码：

A:

#include <cstdio>
#include <cstring>
#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <string>
using namespace std;

class DoubleLetter {
    public:
	string ableToSolve(string S) {
	    while (1) {
		int n = S.length();
		string tmp = "";
		int flag = 1;
		for (int i = 0; i < n - 1; i++) {
		    if (S[i] == S[i + 1]) {
			flag = 0;
			for (int j = 0; j < n; j++) {
			    if (j == i || j == i + 1) continue;
			    tmp += S[j];
			}
			break;
		    }
		}
		if (flag) break;
		S = tmp;
	    }
	    if (S == "") return "Possible";
	    else return "Impossible";
	}
};

B:

#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;

class Egalitarianism3Easy {
public:
    int bitcount(int x) {
	int ans = 0;
	while (x) {
	    ans += (x&1);
	    x >>= 1;
	}
	return ans;
    }

    int maxCities(int n, vector<int> a, vector<int> b, vector<int> len) {
	int g[15][15];
	for (int i = 1; i <= 10; i++)
	    for (int j = 1; j <= 10; j++) {
		if (i == j) g[i][j] = 0;
		else g[i][j] = 1000000000;
	    }
	for (int i = 0; i < n - 1; i++)
	    g[a[i]][b[i]] = g[b[i]][a[i]] = len[i];
	for (int k = 1; k <= n; k++) {
	    for (int i = 1 ; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
		    g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
		}
	    }
	}
	int tmp[15], tn;
	int ans = 1;
	for (int i = 1; i < (1<<n); i++) {
	    tn = 0;
	    for (int j = 0; j < n; j++) {
		if (i&(1<<j)) {
		    tmp[tn++] = j + 1;
		}
	    }
	    int ss = -1;
	    int flag = 0;
	    for (int j = 0; j < tn; j++) {
		for (int k = j + 1; k < tn; k++) {
		    if (ss == -1) ss = g[tmp[j]][tmp[k]];
		    else {
			if (ss != g[tmp[j]][tmp[k]]) {
			    flag = 1;
			    break;
			}
		    }
		}
		if (flag)
		    break;
	    }
	    if (flag == 0) ans = max(ans, bitcount(i));
	}
	return ans;
    }
};

C:

#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
using namespace std;

typedef pair<string, int> pii;

class SuffixArrayDiv2 {
    public:
    string smallerOne(string s) {
	int n = s.length();
	pii save[55];
	for (int i = n - 1; i >= 0; i--) {
	    string tmp = "";
	    for (int j = i; j < n; j++)
		tmp += s[j];
	    save[i].first = tmp;
	    save[i].second = i;
	}
	sort(save, save + n);
	for (int t = 0; t < n; t++) {
	    if (s[t] == 'a') continue;
	    string ss = s;
	    ss[t]--;
	    pii sav[55];
	    for (int i = n - 1; i >= 0; i--) {
		string tmp = "";
		for (int j = i; j < n; j++)
		    tmp += ss[j];
		sav[i].first = tmp;
		sav[i].second = i;
	    }
	    sort(sav, sav + n);
	    int k = 0;
	    for (; k < n; k++)
		if (save[k].second != sav[k].second) break;
	    if (k == n) return "Exists";
	}
	return "Does not exist";
    }
};