一次元リバーシ / 1D Reversi（AtCoder-2146）

Problem Description

Two foxes Jiro and Saburo are playing a game called 1D Reversi. This game is played on a board, using black and white stones. On the board, stones are placed in a row, and each player places a new stone to either end of the row. Similarly to the original game of Reversi, when a white stone is placed, all black stones between the new white stone and another white stone, turn into white stones, and vice versa.

In the middle of a game, something came up and Saburo has to leave the game. The state of the board at this point is described by a string S. There are |S| (the length of S) stones on the board, and each character in S represents the color of the i-th (1≦i≦|S|) stone from the left. If the i-th character in S is B, it means that the color of the corresponding stone on the board is black. Similarly, if the i-th character in S is W, it means that the color of the corresponding stone is white.

Jiro wants all stones on the board to be of the same color. For this purpose, he will place new stones on the board according to the rules. Find the minimum number of new stones that he needs to place.

Constraints

• 1≦|S|≦105
• Each character in S is B or W.

Input

The input is given from Standard Input in the following format:

S

Output

Print the minimum number of new stones that Jiro needs to place for his purpose.

Example

Sample Input 1

BBBWW

Sample Output 1

1
By placing a new black stone to the right end of the row of stones, all white stones will become black. Also, by placing a new white stone to the left end of the row of stones, all black stones will become white.

In either way, Jiro's purpose can be achieved by placing one stone.

Sample Input 2

WWWWWW

Sample Output 2

0
If all stones are already of the same color, no new stone is necessary.

Sample Input 3

WBWBWBWBWB

Sample Output 3

9

题意：若干个棋子放在一行，每次可以在棋子两端放一个 W 或放一个 B，使得新 W/B 到另一块 W/B 之间全部变为 B/W，问最少要放次才能使得所有棋子都变为 W/B

思路：

由于要求最后棋子颜色都变为相同的，每次放一个棋子会使得其到另一块相同的棋子颜色变换，那么这之间的棋子颜色的长度不必考虑，只需要考虑需要变换多少次才能使得颜色相同，因此直接从前向后枚举，记录相邻不相同的个数输出即可

但由于可能一开始颜色就是相同的，那么同时也需要记录颜色相同的个数，如果最后颜色相同的个数与棋子长度相同，那么直接输出 0

Source Program

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