Problem p03994 (C++)

Buggy submission (status: Time Limit Exceeded):

// include
//------------------------------------------
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

// conversion
//------------------------------------------
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i, c)                                                             \
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define EXISTch(s, c)                                                          \
  ((((s).find_first_of(c)) != std::string::npos) ? 1 : 0) // cがあれば1 if(1)
#define SORT(c) sort((c).begin(), (c).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) FOR(i, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = (int)1000000007;
const LL MOD = (LL)1000000007;          // 10^9+7
const LL INF2 = (LL)100000000000000000; // 10^18
const int N = 100010;                   // 10^5+10

const int MAX_N = 2000;
int a[MAX_N], n, x;
int f[MAX_N][MAX_N];

int main() {

  string s;
  int k;
  cin >> s >> k;

  for (int i = 0; i < s.length(); i++) {
    while (s[i] != 'a' && i != s.length() - 1) {
      int d = 26 - (s[i] - 'a');

      if (k - d >= 0) {
        k -= d;
        s[i] = 'a';
      }
    }
  }

  if (s[s.length() - 1] + k <= 'z') {
    s[s.length() - 1] = s[s.length() - 1] + k;

  } else {
    s[s.length() - 1] = s[s.length() - 1] + (k % 26) - 26;
  }

  if (s[s.length() - 1] < 'a')
    s[s.length() - 1] += 26;

  cout << s << endl;

  return 0;
}


Fixed submission:

// include
//------------------------------------------
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

// conversion
//------------------------------------------
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i, c)                                                             \
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define EXISTch(s, c)                                                          \
  ((((s).find_first_of(c)) != std::string::npos) ? 1 : 0) // cがあれば1 if(1)
#define SORT(c) sort((c).begin(), (c).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) FOR(i, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = (int)1000000007;
const LL MOD = (LL)1000000007;          // 10^9+7
const LL INF2 = (LL)100000000000000000; // 10^18
const int N = 100010;                   // 10^5+10

const int MAX_N = 2000;
int a[MAX_N], n, x;
int f[MAX_N][MAX_N];

int main() {

  string s;
  int k;
  cin >> s >> k;

  for (int i = 0; i < s.length(); i++) {
    while (s[i] != 'a' && i != s.length() - 1) {
      int d = 26 - (s[i] - 'a');

      if (k - d >= 0) {
        k -= d;
        s[i] = 'a';
      } else {
        break;
      }
    }
  }

  if (s[s.length() - 1] + k <= 'z') {
    s[s.length() - 1] = s[s.length() - 1] + k;

  } else {
    s[s.length() - 1] = s[s.length() - 1] + (k % 26) - 26;
  }

  if (s[s.length() - 1] < 'a')
    s[s.length() - 1] += 26;

  cout << s << endl;

  return 0;
}