Codeforces 279C

思路：dp[i]表示a[i]之前连续的比a[i]大的数的个数，rdp[i]表示a[i]之后连续的比a[i]大的数的个数。如果dp[st] + rdp[end] >= end - st + 1,则是Yes，否则No。

#include<iostream>
#include<cstdio>
#include<cstring>
#define MAX 100005
using namespace std;
int a[MAX], dp[MAX], rdp[MAX];
int main(){
    int n, Q, st, end;
    /* freopen("in.c", "r", stdin); */
    while(~scanf("%d%d", &n, &Q)){
        memset(dp, 0, sizeof(dp));
        memset(rdp, 0, sizeof(rdp));
        memset(a, 0, sizeof(a));
        for(int i = 1;i <= n;i ++) scanf("%d", &a[i]);
        for(int i = 1; i <= n;i ++){
            if(a[i] <= a[i-1]) dp[i] = dp[i-1] + 1;
            else dp[i] = 1;
        }
        for(int i = n;i >= 1;i --){
            if(a[i] <= a[i+1]) rdp[i] = rdp[i+1] + 1;
            else rdp[i] = 1;
        }
        for(int i = 0;i < Q;i ++){
            scanf("%d%d", &st, &end);
            if(rdp[st] + dp[end] >= end - st + 1) printf("Yes\n");
            else printf("No\n");
        }
    }
    return 0;
}