codeforces 1230B. Ania and Minimizing.cpp

#include<bits/stdc++.h>

using namespace std;

/*** Optimization ***/
#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")

/*** Typedef ***/
typedef long long ll;
typedef unsigned long long ull;

/*** Input Output ***/
#define sci1(a) scanf("%d",&a)
#define sci2(a,b) scanf("%d %d",&a,&b)
#define sc1(a) scanf("%lld",&a)
#define sc2(a,b) scanf("%lld %lld",&a,&b)
#define sc3(a,b,c) scanf("%lld %lld %lld",&a,&b,&c)

#define pf1(a) printf("%d\n",a)
#define pf2(a,b) printf("%d %d\n",a,b)
#define pf1(a) printf("%lld\n",a)
#define pf2(a,b) printf("%lld %lld\n",a,b)

/*** Loops ***/
#define for0(num) for(ll i = 0; i < num; i++)
#define for1(num) for(ll i = 1; i <= num; i++)
#define forr(num) for(ll i = num - 1; i >= 0; i--)
#define forin(arr, num) for(ll i = 0; i < num; i++) sc1(arr[i]);
#define vpnt(ans) for(ll i = 0; i < ans.size(); i++) cout << ans[i] << (i + 1 < ans.size() ? ' ' : '\n');
#define apnt(arr, num) for(ll i = 0; i < num; i++) cout << arr[i] << (i + 1 < num ? ' ' : '\n');

/*** Define Values ***/
#define mx 1000000
#define mod 1000000007
#define PI acos(-1.0)
#define eps 1e-7
#define size1 2005

#define pb push_back
#define ff first
#define ss second
#define mp make_pair
#define mem(name, value) memset(name, value, sizeof(name))

/*** STLs ***/
typedef vector <ll> vll;
typedef set <ll> sll;
typedef multiset <ll> msll;
typedef queue <ll> qll;
typedef map <ll, ll> mll;
typedef pair <ll, ll> pll;
typedef vector <pair <ll , ll> > vpll;

/*** Sorts ***/
#define all(v) (v).begin(), (v).end()
#define rev(v) reverse(all(v))
#define srt(v) sort(all(v))
#define srtGreat(v) sort(all(v), greater<ll>())
inline bool cmp(pll a,pll b){ if(a.ff == b.ff)return a.ss < b.ss; return a.ff > b.ff; }

/*** BitWise Operations
bool getBit (ll num, ll pos) { return num & (1 << pos); } // get bit right -> left
ll setBit (ll num, ll pos) { return num | (1 << pos); }
ll chearBit (ll num, ll pos) { ll mask = ~(1 << pos); return num & mask; }
ll updateBit (ll num, ll pos, bool bit1or0) { ll value = bit1or0 ? 1 : 0; ll mask = ~(1 << pos); return (num & mask) | (value << pos); }
 ***/

/*** Grids ***/
int drx[8] = {-2,-2,-1,-1,1,1,2,2};
int dcy[8] = {-1,1,-2,2,-2,2,-1,1};
int dirx[4] = { -1, 0, 1, 0 };
int diry[4] = { 0, -1, 0, 1 };

/*** Functions
ll BigMod(ll base, ll pow, ll modvalue){ if (pow == 0) return 1;  ll ans = BigMod(base, pow / 2, modvalue);ll total = ((ans % modvalue) * (ans % modvalue)) % modvalue;  if(pow % 2 == 0) return total; else{ return (total * (base % modvalue) ) % modvalue; } }
ll InverseMod(ll base, ll pow) { if(pow == 0) return 1; ll ans = InverseMod(base, pow / 2); ans = (ans * ans) % mod; if(pow & 1){ return (ans * base) % mod; } else{ return ans; } }
bool checkprime(ll num) { if(num < 2) return false; for(ll i = 2; i * i <= num; i++){ if(num % i == 0) return false; } return true; }
ll EularPHI(ll num) { double ans = num; for(ll i = 2; i * i <= num; i++){ if(num % i == 0){ while (num % i == 0) { num /= i; } ans *= (1.0 - (1.0 / (double)i)); } } if(num > 1) ans *= (1.0 - (1.0 / (double)num)); return (ll)ans; }

 ***/
template <class T> inline T gcd(T a,T b){if(b == 0)return a; return gcd(b, a % b);}
template <class T> inline T lcm(T a,T b){return a * b / gcd<T>(a, b);}
template <class T> inline T power(T b,T p){ll ans = 1;while(p--) ans *= b; return ans;}

/*** Some Prints ***/
#define en cout << '\n';
#define no cout << "NO" << '\n'
#define yes cout << "YES" << '\n'
#define case cout << "Case " << t++ << ": "


int main() {

#ifndef ONLINE_JUDGE
    clock_t tStart = clock();
    //freopen("/opt/Coding/clion code/input.txt", "r", stdin);
    //freopen("/opt/Coding/clion code/output.txt", "w", stdout);
#endif

    ll n, m, num, tc, t = 1;

    sc2(num, m);

    string str;
    cin >> str;

    if(num == 1 && m == 1)
        return cout << 0 << endl,0;

    for (ll i = 0; i < num && m; ++i) {
        if(str[i] > '1' && i == 0) {
            str[i] = '1';
            m--;
            continue;
        }
        if(str[i] > '0' && i > 0) {
            str[i] = '0';
            m--;
        }
    }

    cout << str << endl;

#ifndef ONLINE_JUDGE
    printf("\nRun Time -> %.10fs\n", (double)(clock()-tStart) / CLOCKS_PER_SEC);
#endif

}