贪心基础题：
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N = 110;
int n, b;
int a[N], cost[N];//存储代价
int main(){
cin>>n>>b;
for(int i = 1; i<=n; i++) cin>>a[i];
int odd = 0, even = 0, cnt = 0;
for(int i = 1; i<n; i++){//遍历
if(a[i]%2==0) even ++ ;
else odd ++ ;
if(odd == even) cost[cnt++] = abs(a[i+1]-a[i]);
}
sort(cost, cost+cnt);//代价从小到大
int res = 0, sum = 0;
for(int i = 0; i<cnt; i++){
sum += cost[i];
if(sum > b) break;
res ++ ;
}
cout<<res;
return 0;
} 分类讨论：
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N = 200010;
int n;
int w[N];
int main(){
cin>>n;
for(int i = 1; i<=n; i++) cin>>w[i];
int res = 0, last = 0;//刚刚弹出的元素
for(int i = 1, j = n; i<=j; ){//左右指针模拟队列
//分类讨论
if(w[i] != w[j]){
if(w[i] < w[j]){
if(w[j] <= last) break;
if(w[i] <= last) last = w[j--];
else last = w[i++];
res ++ ;
}
else{
if(w[i] <= last) break;
if(w[j] <= last) last = w[i++];
else last = w[j--];
res ++ ;
}
}
else{
//从左和从右 都枚举一遍
int left = 0, tmp = last;
for(int k = i; k<=j; k++){
//k从左到右检查
if(w[k] > tmp) tmp = w[k], left++;
else break;
}
int right = 0;
tmp = last;
for(int k = j; k>=i; k--){
if(w[k] > tmp) tmp = w[k], right++;
else break;
}
res += max(left, right);
break;
}
}
cout<<res;
return 0;
} 
