Suffix Rotation
Problem Statement :
Megan is playing a string game with the following rules: It starts with a string, s. During each turn, she performs the following move: Choose an index in s. The chosen index must be strictly greater than any index chosen in a prior move. Perform one or more circular rotations (in either direction) of the suffix starting at the chosen index. For example, let's say s = abcdefjghi. During our move, we choose to do three right rotations of the suffix starting at index 6: image Note that this counts as one move. The goal of the game is to convert s into the lexicographically smallest possible string in as few moves as possible. In other words, we want the characters to be in alphabetical order. Megan plays this game g times, starting with a new string s each time. For each game, find the minimum number of moves necessary to convert s into the lexicographically smallest string and print that number on a new line. Input Format The first line contains an integer, g, denoting the number of games. Each of the g subsequent lines contains a single string denoting the initial value of string s for a game. Constraints 1 <= g <= 100 1 <= |s| <= 1000 s consists of lowercase English alphabetic letters only. Output Format For each game, print an integer on a new line denoting the minimum number of moves required to convert s into the lexicographically smallest string possible.
Solution :
Solution in C :
In C++ :
#include <bits/stdc++.h>
using namespace std;
#define N 1010
#define inf 1010
int t;
char s[N];
map <string, int> mp;
int solve(char *s) {
// puts(s);
int len = strlen(s);
if (!len) return 0;
if (mp.count(s)) return mp[s];
char c = *min_element(s, s + len);
if (s[0] == c) return mp[s] = solve(s + 1);
int rlt = 0;
char ss[N];
int runs = 0;
bool vis[N];
for (int i = 0; i < len; i ++) if (s[i] != c) {
ss[runs] = s[i];
int prv = i ? i - 1 : len - 1;
vis[runs++] = s[prv] == c;
if (i < len - 1 && s[i+1] == c) rlt ++;
}
ss[runs] = 0;
len = runs;
c = *min_element(ss, ss + len);
bool start_c = 0;
for (int i = 0; i < len; i ++) {
if (vis[i] && ss[i] == c) {
start_c = 1; break;
}
}
int mn = inf;
char sss[N];
for (int i = 0; i < len; i ++) if (vis[i]) {
if (start_c && ss[i] != c) continue;
for (int j = 0; j < len; j ++) sss[j] = ss[(j+i)%len];
sss[len] = 0;
mn = min(mn, solve(sss));
}
return mp[s] = rlt + mn;
}
int main() {
// freopen("s.in", "r", stdin);
// freopen("s.out", "w", stdout);
scanf("%d", &t);
while (t --) {
scanf("%s", s);
printf("%d\n", solve(s));
}
return 0;
}
In Java :
import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution {
static class SH {
int id=0;
int[] cnt;
String cs;
SH(String s,int[] ant) {
cs=s;
cnt=Arrays.copyOf(ant,26);
prep();
}
void prep() {
StringBuilder sb=new StringBuilder();
while(id<cs.length()) {
char mc=getMC();
if(mc==cs.charAt(id)) {
++id;
--cnt[mc-'a'];
}
else break;
}
/*
for(int i=id;i<chs.length;++i) {
if(i!=id&&chs[i]==chs[i-1]) {
--cnt[chs[i]-'a'];
} else {
sb.append(chs[i]);
}
}
cs=sb.toString();
*/
cs=cs.substring(id);
id=0;
}
public int mm(){
if(hm.containsKey(cs)) return hm.get(cs);
if(0==cs.length()) return 0;
char mc=getMC();
String[] stx=cs.split(""+mc);
int res=0;
cnt[mc-'a']=0;
StringBuilder sb=new StringBuilder();
for(String x:stx) {
if(x.length()!=0) {
sb.append(x);
++res;
}
}
if(cs.charAt(cs.length()-1)!=mc) --res;
mc=getMC();
String ns="";
int mt=sb.length();
int j=0;
HashSet<String> hs=new HashSet();
for(String bx:stx) {
if(j==res) break;
if(bx.length()==0) continue;
sb.delete(0,bx.length());
sb.append(bx);
String ts=sb.toString();
int tmt=cMC(ts,mc);
if(tmt<mt) {
ns=ts;
mt=tmt;
hs.clear();
hs.add(ts);
} else if(tmt==mt) {
hs.add(ts);
}
++j;
}
int rm=Integer.MAX_VALUE;
for(String bx:hs) {
int nm=new SH(bx,cnt).mm();
if(nm<rm) rm=nm;
}
res+=rm;
hm.put(cs,res);
return res;
}
int cMC(String st,char x) {
int res=0;
String[] nxt=st.split(""+x);
for(String tt:nxt) {
if(tt.length()!=0) ++res;
}
if(st.charAt(st.length()-1)!=x) --res;
if(st.charAt(0)==x) --res;
return res;
}
char getMC() {
for(char x='a';x<='z';++x) {
if(cnt[x-'a']!=0) return x;
}
return '*';
}
}
static HashMap<String,Integer> hm=new HashMap();
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int q = in.nextInt();
for(int a0 = 0; a0 < q; a0++){
String s = in.next();
int[] cnt=new int[26];
for(char x:s.toCharArray()) ++cnt[x-'a'];
// your code goes here
SH t=new SH(s,cnt);
System.out.println(t.mm());
}
}
}
In C :
#include<stdio.h>
#include<string.h>
#include<stdbool.h>
#define FOR(a,b,c) for(int a=(b),_for=(c);a<_for;++a)
#define M 1000
#define Z 26
char c[M+5];
int n, P[M+5], A[M+5], B[M+5], C[Z+5], D[M+5], E[M+5];
int min(int a, int b)
{
return a < b ? a : b;
}
int n;
int p[M+5];
char c[M+5];
int cnt[Z+5];
int dp[M+5];
int nju[M+5];
int nx[M+5];
int isti[M+5];
void solve(){
scanf ("%s",c);
n=strlen(c);
FOR(i,0,n) p[i]=Z-1-(c[i]-'a');
FOR(i,0,Z) cnt[i]=0;
FOR(i,0,n) cnt[p[i]]++;
FOR(i,0,n) dp[i]=0;
FOR(i,0,n) nju[i]=0;
FOR(i,0,n) nx[i]=0;
FOR(i,0,n) isti[i]=0;
FOR(cl,0,Z){
if (!cnt[cl]) continue;
FOR(i,0,n) dp[i]=nju[i];
memset(nju,-1,n*sizeof(int));
memset(isti,0,n*sizeof(int));
int last=-1,prvi=-1,sum=0,b1=n,b2=n;
FOR(i,0,n) if (p[i]<=cl){
if (last>=0){
nx[last]=i;
if (p[last]!=p[i] && p[i]==cl) isti[i]=1,sum++;
}
else prvi=i;
last=i;
}
nx[last]=prvi;
// FOR(i,0,n) printf ("%d -> %d\n",i,nx[i]);
if (p[last]!=p[prvi] && p[prvi]==cl) isti[prvi]=1,sum++;
int pb1=-1;
FOR(i,0,n) if (p[i]==cl && p[nx[i]]!=cl){
b2=min(b2,dp[nx[i]]);
// printf ("%d -> %d\n",i,b2);
if (b2<b1)
{
int temp = b1;
b1 = b2;
b2 = temp;
pb1=i;
}
}
// printf ("%d %d %d ???\n",sum,b1,pb1);
sum+=b1-1;
if (pb1==-1) sum=-1;
bool flag=0;
FOR(i,0,n){
if (p[i]>cl) continue;
if (p[i]<cl || !isti[i]){
nju[i]=sum+1;
continue;
}
if (b1==b2 || b2==n){
nju[i]=sum;
continue;
}
nju[i]=sum;
flag=1;
}
if (flag){
for (int i=pb1;i>=0 && flag;--i){
if (isti[i]) nju[i]++,flag=0;
}
for (int i=n-1;i>=0 && flag;--i){
if (isti[i]) nju[i]++,flag=0;
}
}
// FOR(i,0,n) printf ("%d %d %d\n",i,isti[i],nju[i]);
// printf ("\n");
}
printf ("%d\n",nju[0]);
}
int main(){
int znj;
scanf ("%d",&znj);
while(znj--) solve();
return 0;
}
In Python3 :
#!/bin/python3
import sys
def bestlastrotation(s,groups,letters,memos):
if len(letters) < 3:
return groups[0]
mn = letters[0]
mn2 = letters[1]
mn3 = letters[2]
lens = len(s)
groups2 = []
for g in groups:
i = g
while s[i] == mn:
i = (i + 1) % lens
if s[i] == mn2 and s[g-1] != mn2:
groups2.append([g,i])
if len(groups2) == 0: return groups[0]
if len(groups2) == 1: return groups2[0][0]
for gg in groups2:
j = gg[1]
while s[j] == mn2 or s[j] == mn:
j = (j + 1) % lens
if s[j] != mn3:
return gg[0]
else:
gg.append(j)
if len(letters) < 4:
return groups2[0][0]
groupset = set(x[0] for x in groups2)
ans = 0
best = lens
for g in groupset:
s2 = (s[g:]+s[:g]).replace(mn,'')
result = min_rotations(s2,memos)
if best > result:
best = result
ans = g
return ans
def min_rotations(s,memos):
if s in memos:
return memos[s]
letters = sorted(set(s))
mn = min(letters)
ans = 0
while mn != max(letters):
i = 0
while s[i] == mn:
i += 1
if i > 0:
s = s[i:]
groups = []
for i in range(len(s)):
if s[i] == mn and s[i-1] != mn:
groups.append(i)
ans += len(groups)
if len(groups) == 1:
g = groups[0]
s = s[g:] + s[:g]
if len(groups) > 1:
g = bestlastrotation(s,groups,letters,memos)
s = s[g:] + s[:g]
s = s.replace(mn,'')
letters = letters[1:]
mn = min(letters)
memos[s] = ans
return ans
q = int(input().strip())
for a0 in range(q):
s = input().strip()
# your code goes here
print(min_rotations(s,dict()))
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