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Create 3677.Count-Binary-Palindromic-Numbers.cpp

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Binary_Search/3677.Count-Binary-Palindromic-Numbers
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	`1`	`+using LL = long long;`
	`2`	`+class Solution {`
	`3`	`+public:`
	`4`	`+ LL reverseBits(LL x) {`
	`5`	`+ LL r = 0;`
	`6`	`+ while (x>0) {`
	`7`	`+ r = r*2+(x&1);`
	`8`	`+ x>>=1;`
	`9`	`+ }`
	`10`	`+ return r;`
	`11`	`+ }`
	`12`	`+`
	`13`	`+ LL build(LL half, int L) {`
	`14`	`+ int h = (L+1)/2;`
	`15`	`+ int k = L-h;`
	`16`	`+ if (L%2==0) {`
	`17`	`+ return (half<<k) \| reverseBits(half);`
	`18`	`+ } else {`
	`19`	`+ return (half<<k) \| reverseBits(half>>1);`
	`20`	`+ }`
	`21`	`+ }`
	`22`	`+`
	`23`	`+ int countBinaryPalindromes(long long n) {`
	`24`	`+ if (n==0) return 1;`
	`25`	`+ int maxLen = floor(log2(n)) + 1;`
	`26`	`+`
	`27`	`+ LL ret = 1;`
	`28`	`+ for (int L=1; L<maxLen; L++) {`
	`29`	`+ int h = (L+1)/2;`
	`30`	`+ long long mn = 1LL<<(h-1);`
	`31`	`+ long long mx = (1LL<<h)-1;`
	`32`	`+ ret += mx-mn+1;`
	`33`	`+ }`
	`34`	`+`
	`35`	`+ {`
	`36`	`+ int L = maxLen;`
	`37`	`+ int h = (L+1)/2;`
	`38`	`+ long long mn = 1LL<<(h-1);`
	`39`	`+ long long mx = (1LL<<h)-1;`
	`40`	`+ LL lo = mn, hi = mx;`
	`41`	`+ while (lo < hi) {`
	`42`	`+ LL mid = hi-(hi-lo)/2;`
	`43`	`+ LL pal = build(mid, L);`
	`44`	`+ if (pal <= n) {`
	`45`	`+ lo = mid;`
	`46`	`+ } else {`
	`47`	`+ hi = mid-1;`
	`48`	`+ }`
	`49`	`+ }`
	`50`	`+ LL pal = build(hi, L);`
	`51`	`+ if (pal <= n)`
	`52`	`+ ret += (LL)(hi-mn+1);`
	`53`	`+ }`
	`54`	`+`
	`55`	`+ return ret;`
	`56`	`+ }`
	`57`	`+};`

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