B - Sort the Array

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找出一個遞減序列，如果有兩個或兩個以上遞減序列直接no了，然後對遞減序列兩端數start，end，然後比較a[start]和a[end+1] ， a[end] 和a[start-1]

#include<iostream>
#include<stdio.h>
using namespace std;
int a[100005];
int main(){
   // freopen("in.txt","r",stdin);
    int n;
    while(~scanf("%d",&n)){
        a[0]=-1;
        a[n+1]=1000000009;
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
        int start=-1,end=-1,flag=0;
        for(int i=2;i<=n+1;i++){
            if(a[i-1]>a[i] && start==-1){
                start=i-1;
            }
            else if(start!=-1 && end==-1 && a[i-1]<a[i]){
                end=i-1;
                flag=1;
            }
            else if(a[i-1]>a[i] && start!=-1 && end!=-1){
                flag=2;
                break;
            }
        }
   //     cout<<"初始位置："<<start<<" "<<end<<endl;
        if(n==1 || start==end){
            cout<<"yes"<<endl;
            cout<<"1 1"<<endl;
        }
        else if(flag==2){
            cout<<"no"<<endl;
        }
        else if(a[start]<a[end+1] && a[end]>a[start-1]){
            cout<<"yes"<<endl;
            cout<<start<<" "<<end<<endl;
        }
        else
            cout<<"no"<<endl;
    }
}