#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
LL reach(vector<LL> a, vector<LL> b){
if(a[0] < b[0]) return 0;
vector<pair<LL,LL> > acompress, bcompress;
LL acur = a[0];
LL curmin = a[0];
for(LL i = 0; i < a.size(); i++){
if(a[i] >= acur){
acompress.push_back({acur, curmin});
acur = a[i];
curmin = a[i];
}
curmin = min(curmin, a[i]);
}
LL bcur = b[0];
LL curmax = b[0];
for(LL i = 0; i < b.size(); i++){
if(b[i] <= bcur){
bcompress.push_back({bcur, curmax});
bcur = b[i];
curmax = b[i];
}
curmax = max(curmax, b[i]);
}
LL i = 0;
LL j = 0;
while(i < acompress.size() - 1 && j < bcompress.size() - 1){
if(bcompress[j+1].second <= acompress[i].first){
j++;
} else if(bcompress[j].first <= acompress[i+1].second){
i++;
} else {
return 0;
}
}
return 1;
}
LL okay(vector<LL> a, vector<LL> b){
LL ma = 0;
LL mb = 0;
for(LL j = 0; j < a.size(); j++){
if(a[j] > a[ma]) ma = j;
}
for(LL j = 0; j < b.size(); j++){
if(b[j] < b[mb]) mb = j;
}
if(a[ma] < b[mb]) return 0;
vector<LL> la, lb;
vector<LL> ra, rb;
for(LL j = 0; j <= ma; j++) la.push_back(a[j]);
for(LL j = a.size()-1; j >= ma; j--) ra.push_back(a[j]);
for(LL j = 0; j <= mb; j++) lb.push_back(b[j]);
for(LL j = b.size()-1; j >= mb; j--) rb.push_back(b[j]);
return ok(la, lb) && ok(ra, rb);
return reach(la, lb) && reach(ra, rb);
}
LL ok(vector<LL> a, vector<LL> b){
LL dp[a.size()][b.size()];
for(int i = 0; i < a.size(); i++){
for(int j = 0; j < b.size(); j++){
dp[i][j] = 0;
if(a[i] >= b[j]){
if((i == 0 && j == 0) || (i > 0 && dp[i-1][j]) || (j > 0 && dp[i][j-1])){
dp[i][j] = 1;
}
}
}
}
return dp[a.size()-1][b.size()-1];
}
int main(){
cin.sync_with_stdio(0); cin.tie(0);
LL n, k, t;
cin >> n >> k >> t;
k--;
vector<LL> x(n);
for(LL i = 0; i < n; i++){
cin >> x[i];
}
LL s = -1;
LL e = 1000000000;
while(s + 1 < e){
LL m = (s + e) / 2;
vector<LL> y = x;
for(LL i = 0; i < n; i++){
y[i] -= m * t * 2 * i;
}
vector<LL> a, b;
for(LL i = k; i >= 0; i--){
a.push_back(y[i]);
}
for(LL i = k; i < n; i++){
b.push_back(y[i]);
}
if(ok(a,b)){
e = m;
} else {
s = m;
}
}
cout << e << '\n';
}
Compilation message
sparklers.cpp: In function 'LL reach(std::vector<long long int>, std::vector<long long int>)':
sparklers.cpp:10:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(LL i = 0; i < a.size(); i++){
~~^~~~~~~~~~
sparklers.cpp:20:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(LL i = 0; i < b.size(); i++){
~~^~~~~~~~~~
sparklers.cpp:30:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
while(i < acompress.size() - 1 && j < bcompress.size() - 1){
~~^~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:30:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
while(i < acompress.size() - 1 && j < bcompress.size() - 1){
~~^~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp: In function 'LL okay(std::vector<long long int>, std::vector<long long int>)':
sparklers.cpp:45:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(LL j = 0; j < a.size(); j++){
~~^~~~~~~~~~
sparklers.cpp:48:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(LL j = 0; j < b.size(); j++){
~~^~~~~~~~~~
sparklers.cpp:58:9: error: 'ok' was not declared in this scope
return ok(la, lb) && ok(ra, rb);
^~
sparklers.cpp: In function 'LL ok(std::vector<long long int>, std::vector<long long int>)':
sparklers.cpp:63:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0; i < a.size(); i++){
~~^~~~~~~~~~
sparklers.cpp:64:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int j = 0; j < b.size(); j++){
~~^~~~~~~~~~
