Codeforces Round 736 (Div. 2)
B
Gregor and the Pawn Game
Codeforces
800
原题
← AC →
翻译中…

There is a chessboard of size $n$ by $n$. The square in the $i$-th row from top and $j$-th column from the left is labelled $(i,j)$.

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Currently, Gregor has some pawns in the $n$-th row. There are also enemy pawns in the $1$-st row. On one turn, Gregor moves one of his pawns. A pawn can move one square up (from $(i,j)$ to $(i-1,j)$) if there is no pawn in the destination square. Additionally, a pawn can move one square diagonally up (from $(i,j)$ to either $(i-1,j-1)$ or $(i-1,j+1)$) if and only if there is an enemy pawn in that square. The enemy pawn is also removed.

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Gregor wants to know what is the maximum number of his pawns that can reach row $1$?

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Note that only Gregor takes turns in this game, and the enemy pawns never move. Also, when Gregor's pawn reaches row $1$, it is stuck and cannot make any further moves.

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Input

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The first line of the input contains one integer $t$ ($1\le t\le 2\cdot 10^4$) — the number of test cases. Then $t$ test cases follow.

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Each test case consists of three lines. The first line contains a single integer $n$ ($2\le n\le 2\cdot{10}^{5}$) — the size of the chessboard.

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The second line consists of a string of binary digits of length $n$, where a $1$ in the $i$-th position corresponds to an enemy pawn in the $i$-th cell from the left, and $0$ corresponds to an empty cell.

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The third line consists of a string of binary digits of length $n$, where a $1$ in the $i$-th position corresponds to a Gregor's pawn in the $i$-th cell from the left, and $0$ corresponds to an empty cell.

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It is guaranteed that the sum of $n$ across all test cases is less than $2\cdot{10}^{5}$.

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Output

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For each test case, print one integer: the maximum number of Gregor's pawns which can reach the $1$-st row.

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Note

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In the first example, Gregor can simply advance all $3$ of his pawns forward. Thus, the answer is $3$.

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In the second example, Gregor can guarantee that all $4$ of his pawns reach the enemy row, by following the colored paths as demonstrated in the diagram below. Remember, only Gregor takes turns in this "game"!

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image

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In the third example, Gregor's only pawn is stuck behind the enemy pawn, and cannot reach the end.

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In the fourth example, Gregor has no pawns, so the answer is clearly $0$.

翻译中…

样例

Input #1
4
3
000
111
4
1111
1111
3
010
010
5
11001
00000
Output #1
3
4
0
0
InputCopy OutputCopy
题目信息
题号
1549B
时间限制
1 s
内存限制
256 MB
标签
DFS 及类似
动态规划
网络流
图匹配
图论
贪心
模拟

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。