hdu-5661 Claris and XOR (greedy)

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Claris and XOR

Time limit:2000/1000 MS (java/others)

Memory limit:65536/65536 K (java/others)

Problem Descriptionclaris loves bitwise operations very much, especially XOR, because it has many beautiful features. He gets four positive integersa,b,c,D that satisfiesa≤b andc≤d . He wants to choose, integersx,y that satisfiesa≤x≤b andc≤y≤d , and maximize the value ofx xOR y . But he doesn ' t know how to does it, so please tell him the maximum value ofx xOR y.

Inputthe first line contains an integerT(1≤t≤ten) --the number of the test cases.
For each test case, the only line contains four integersA,B,c, D ( 1≤a ,b , c, D≤ 1018) . Between each of the adjacent integers there are a white space separated.

Outputfor Each test case, the only line contains a integer that is the maximum value of x xOR y.

Sample Input21 2 3 45 7 13 15

Sample output611  Test Instructions:  asked a<=x<=b,c<=y<=d; the largest x^y value is how much;  ideas:  greedy, from high to low, can take 1 of 1 can not take 0, Update the value of the a,b,c,d at the same time; &NBSP;AC code: 

#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include < cmath> #include <bits/stdc++.h> #include <stack> #include <map> using namespace std; #define for (i,j,n) for (int i=j;i<=n;i++) #define MST (SS,B) memset (ss,b,sizeof (ss)); typedef long Long LL;    Template<class t> void Read (t&num) {char CH; bool F=false; For (Ch=getchar (); ch< ' 0 ' | | Ch> ' 9 ';    f= ch== '-', Ch=getchar ()); for (num=0;    ch>= ' 0 ' &&ch<= ' 9 '; num=num*10+ch-' 0 ', Ch=getchar ()); F && (num=-num);}    int stk[70], tp;template<class t> inline void print (T p) {if (!p) {puts ("0"); return;}    while (p) stk[++ TP] = p%10, p/=10;    while (TP) Putchar (stk[tp--] + ' 0 '); Putchar (' \ n ');} Const LL Mod=1e9+7;const double Pi=acos ( -1.0); const int INF=1E18;CONST int N=1e5+10;const int Maxn=5e3+4;const double eps= 1e-12;    LL A,b,c,d;int Main () {//freopen ("In.txt", "R", stdin);    int T;    Read (T); while (t--) {Read (a); Read (b); Read (c); Read (d);        LL ans=0; for (int i=63;i>=0;i--) {int fa= ((a>>i) &1), fb= ((b>>i) &1), fc= ((c>>i) &1),            Fd= ((d>>i) &1);            if (FA!=FB&AMP;&AMP;FC!=FD) {ans|= (1ll<< (i+1)) -1;break;}                else if (FA!=FB) {ans|= (1ll<<i);                    if (FC) {b= (1ll<<i)-1;                    c-= (1ll<<i);                d-= (1ll<<i);                    } else {a=0;                b-= (1ll<<i);                }} else if (FC!=FD) {ans|= (1ll<<i);                    if (FA) {d= (1ll<<i)-1;                    a-= (1ll<<i);                b-= (1ll<<i);                    } else {c=0; d-= (1LL&LT;<i);                    }} else {if (FA==FC) {if (FA)                        {LL temp= (1ll<<i);                        A-=temp;                        B-=temp;                        C-=temp;                    D-=temp;                    }} else {ans|= (1ll<<i);                        if (FA) {a-= (1ll<<i);                    b-= (1ll<<i);                        } else {c-= (1ll<<i);                    d-= (1ll<<i);    }}}} print (ANS); } return 0;}

　　

hdu-5661 Claris and XOR (greedy)