分奇偶

奇数项平均值存在且为整数，与偶数项相等

使用s1,s2记录奇数项与偶数项的和，使用n1,n2记录奇数项和偶数项的项数。

核心代码

有注释

tt=read_();
//s应为longlong，否则溢出（被坑了）
s1=0;n1=0;s2=0;n2=0;
while(tt--){
    s2+=read_();n2++;
    //合并偶数/奇数操作，使用if排除奇数项与偶数项不相等的情况
    if(tt--){s1+=read_();n1++;}else{break;}
}
//首先保证整除
if(s2%n2){write_str("NO\n");continue;}
if(s1%n1){write_str("NO\n");continue;}
//其次判断相等
if(s1/n1==s2/n2)write_str("YES\n");else write_str("NO\n");

AC代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>
#define N1 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1
#define N2 N1,N1,N1,N1,N1,N1,N1,N1,N1,N1
#define N3 N2,N2,N2,N2,N2,N2,N2,N2,N2,N2
#define N4 N3,N3,N3,N3,N3,N3,N3,N3,N3,N3
#define D(a) a,1##a,2##a,3##a,4##a,5##a,6##a,7##a,8##a,9##a
#define S246 N2,N2,N1,N1,N1,N1,-1,-1,-1,-1,-1,-1
const int _mp[0x10000] = { N4,N3,N3,N2,N2,N2,N1,N1,N1,-1,-1,-1,-1,-1,-1, D(0),S246,D(1),S246,D(2),S246,D(3),S246,D(4),S246, D(5),S246,D(6),S246,D(7),S246,D(8),S246,D(9), N4,N4,N4,N4,N4,N2,N2,N2,N2,N2,N2,N2,N2,N1,N1,N1,N1,N1,N1,N1,N1, -1,-1,-1,-1,-1,-1 };
#undef N1
#undef N2
#undef N3
#undef N4
#undef D
#undef S246
char *buf_ptr; char *buf_end; char out_buf[1 << 20]; char *pp = out_buf; void io_init(){ struct stat sb; fstat(0,&sb); buf_ptr=(char*)mmap(NULL,sb.st_size,PROT_READ,MAP_PRIVATE,0,0); buf_end=buf_ptr+sb.st_size; } int read_(){ int x=0,f=0; while(buf_ptr<buf_end && *buf_ptr<=' ') buf_ptr++; if(buf_ptr>=buf_end) return 0; if(*buf_ptr=='-'){ f=1; buf_ptr++; } while(buf_ptr+1<buf_end){ int v=_mp[*(uint16_t*)buf_ptr]; if(v==-1) break; x = x*100 + v; buf_ptr += 2; } if(buf_ptr<buf_end && *buf_ptr>='0' && *buf_ptr<='9'){ x = x*10 + (*buf_ptr - '0'); buf_ptr++; } return f ? -x : x; } void push(char c){ if(pp - out_buf == (1<<20)){ fwrite(out_buf,1,1<<20,stdout); pp = out_buf; } *pp++ = c; } void write_(int x){ if(x<0){ push('-'); x = -x; } static int sta[40]; int top=0; do{ sta[top++] = x%10; x/=10; } while(x); while(top) push(sta[--top] + '0'); } void write_str(const char* s){ while(*s) push(*s++); } void io_flush(){ fwrite(out_buf,1,pp - out_buf,stdout); }
int gc(){return(unsigned char)*buf_ptr++;}
static inline void mvp(int n){buf_ptr+=n;}
int main() {
    io_init();
    int t,tt,n1,n2;
    long long s1,s2;
    t=read_();
    while(t--){
        tt=read_();
        s1=0;n1=0;s2=0;n2=0;
        while(tt--){
            s2+=read_();n2++;
            if(tt--){s1+=read_();n1++;}else{break;}
        }
        if(s2%n2){write_str("NO\n");continue;}
        if(s1%n1){write_str("NO\n");continue;}
        if(s1/n1==s2/n2)write_str("YES\n");else write_str("NO\n");
    }
    io_flush();
    return 0;
}