diff options
Diffstat (limited to 'can_i_win.c')
-rw-r--r-- | can_i_win.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/can_i_win.c b/can_i_win.c new file mode 100644 index 0000000..a13c90e --- /dev/null +++ b/can_i_win.c @@ -0,0 +1,48 @@ +// 464. Can I Win +#include "leetcode.h" + +/* + * in the 100 game two players take turns adding, to a running total, any + * integer from 1 to 10. the player who first causes the running total to reach + * or exceed 100 wins. what if we change the same so that players cannot re-use + * integers? for example, two players might take turns drawing from a common + * pool of numbers from 1 to 15 without replacement until they reach a total >= + * 100. given two integers 'maxChoosableInteger' nad 'desiredTotal', return true + * if the first player to move can force a win, otherwise, return false. assume + * both players play optimally. + */ + +static int mem[1 << 20] = {}; + +bool dfs(int maxChoosableInteger, int desiredTotal, int k) { + if (mem[k]) + return mem[k] > 0; + if (desiredTotal <= 0) + return false; + for (int i = 0; i < maxChoosableInteger; ++i) + if (!(k & (1 << i)) & + !dfs(maxChoosableInteger, desiredTotal - i - 1, k | (1 << i))) { + mem[k] = 1; + return true; + } + mem[k] = -1; + return false; +} + +bool canIWin(int maxChoosableInteger, int desiredTotal) { + int sum = maxChoosableInteger * (maxChoosableInteger + 1) / 2; + if (desiredTotal < 2) + return true; + else if (sum < desiredTotal) + return false; + else if (sum == desiredTotal) + return maxChoosableInteger % 2; + else + return dfs(maxChoosableInteger, desiredTotal, 0); +} + +int main() { + printf("%d\n", canIWin(10, 11)); // expect: 0 + printf("%d\n", canIWin(10, 0)); // expect: 1 + printf("%d\n", canIWin(10, 1)); // expect: 1 +} |