实现功能：输入一个长度为N的由26个大写字母组成的字符串，输入M条指令："1 x y"，将x到y的字串重组构成一个字典序最小的回文串，如果不能构成回文串输出False，否则True并完成变换；"2 x y"输出从x到y的子串；"3 x y t"将x到y的所有字全部变成chr(t+64)（即对应大写字母）
原理：用一个数组维护字母个数即可，然后再附带一个带tag的区间覆盖操作，实现回文串的重组
1 type 2 vec=array[0..26] of longint; 3 var 4 i,j,k,l,m,n,t:longint; 5 a:array[0..500000] of vec; 6 b:array[0..500000] of longint; 7 c:array[0..500000] of ansistring; 8 function empty:vec;inline; 9 var a1:vec; 10 begin 11 fillchar(a1,sizeof(a1),0); 12 exit(a1); 13 end; 14 function merge(a1,a2:vec):vec;inline; 15 var i:longint; 16 begin 17 for i:=1 to 26 do a1[i]:=a1[i]+a2[i]; 18 exit(a1); 19 end; 20 function max(x,y:longint):longint;inline; 21 begin 22 if x>y then max:=x else max:=y; 23 end; 24 function min(x,y:longint):longint;inline; 25 begin 26 if x<y then min:=x else min:=y; 27 end; 28 function strr(x:longint;y:char):ansistring;inline; 29 var s1:ansistring;i:longint; 30 begin 31 s1:=''; 32 for i:=1 to x do s1:=s1+y; 33 exit(s1); 34 end; 35 procedure ext(z,x,y:longint);inline; 36 begin 37 if b[z]=0 then exit; 38 if (x<>y) then 39 begin 40 b[z*2]:=b[z]; 41 a[z*2]:=empty; 42 a[z*2][b[z*2]]:=(x+y) div 2-x+1; 43 c[z*2]:=strr((x+y) div 2-x+1,chr(b[z]+64)); 44 b[z*2+1]:=b[z]; 45 a[z*2+1]:=empty; 46 a[z*2+1][b[z*2+1]]:=y-(x+y) div 2; 47 c[z*2+1]:=strr(y-(x+y) div 2,chr(b[z]+64)); 48 end; 49 a[z]:=empty; 50 a[z][b[z]]:=y-x+1; 51 c[z]:=strr(y-x+1,chr(b[z]+64)); 52 b[z]:=0; 53 end; 54 55 procedure built(z,x,y:longint); 56 var c1:char; 57 begin 58 if x=y then 59 begin 60 read(c1);c1:=upcase(c1);c[z]:=c1; 61 a[z]:=empty;a[z][ord(c1)-64]:=1; 62 end 63 else 64 begin 65 built(z*2,x,(x+y) div 2); 66 built(z*2+1,(x+y) div 2+1,y); 67 c[z]:=c[z*2]+c[z*2+1]; 68 a[z]:=merge(a[z*2],a[z*2+1]); 69 end; 70 b[z]:=0; 71 end; 72 function getsum(z,x,y,l,r:longint):vec; 73 var a1:vec; 74 begin 75 if l>r then exit(empty); 76 if b[z]>0 then 77 begin 78 a1:=empty; 79 a1[b[z]]:=r-l+1; 80 exit(a1); 81 end; 82 if (x=l) and (y=r) then exit(a[z]); 83 getsum:=merge(getsum(z*2,x,(x+y) div 2,l,min(r,(x+y) div 2)),getsum(z*2+1,(x+y) div 2+1,y,max((x+y) div 2+1,l),r)); 84 end; 85 procedure cover(z,x,y,l,r,t:longint); 86 begin 87 if l>r then exit; 88 if (x=l) and (y=r) then 89 begin 90 b[z]:=t; 91 a[z]:=empty;a[z][b[z]]:=r-l+1; 92 c[z]:=strr(r-l+1,chr(64+b[z])); 93 exit; 94 end; 95 ext(z,x,y); 96 cover(z*2,x,(x+y) div 2,l,min(r,(x+y) div 2),t); 97 cover(z*2+1,(x+y) div 2+1,y,max((x+y) div 2+1,l),r,t); 98 c[z]:=c[z*2]+c[z*2+1]; 99 a[z]:=merge(a[z*2],a[z*2+1]); 100 end; 101 function setup(x,y:longint):boolean; 102 var a1:vec;i,j,k,l:longint; 103 begin 104 a1:=getsum(1,1,n,x,y); 105 l:=0; 106 for i:=1 to 26 do 107 if odd(a1[i]) then 108 if l=0 then l:=i else exit(false); 109 j:=x;k:=y; 110 for i:=1 to 26 do 111 begin 112 cover(1,1,n,j,j+a1[i] div 2-1,i); 113 cover(1,1,n,k-a1[i] div 2+1,k,i); 114 j:=j+a1[i] div 2;k:=k-a1[i] div 2; 115 end; 116 if l>0 then cover(1,1,n,j,k,l); 117 exit(true); 118 end; 119 function getstr(z,x,y,l,r:longint):ansistring;inline; 120 begin 121 if l>r then exit(''); 122 if b[z]>0 then exit(strr(r-l+1,chr(b[z]+64))); 123 if (x=l) and (y=r) then exit(c[z]); 124 exit(getstr(z*2,x,(x+y) div 2,l,min(r,(x+y) div 2))+getstr(z*2+1,(x+y) div 2+1,y,max((x+y) div 2+1,l),r)); 125 end; 126 begin 127 readln(n,m); 128 built(1,1,n); 129 readln; 130 for i:=1 to m do 131 begin 132 read(t); 133 case t of 134 1:begin 135 readln(j,k); 136 writeln(setup(j,k)); 137 end; 138 2:begin 139 readln(j,k); 140 writeln(getstr(1,1,n,j,k)); 141 end; 142 3:begin 143 readln(j,k,l); 144 cover(1,1,n,j,k,l); 145 end; 146 end; 147 end; 148 end.