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// ----------------- solution 1: 使用异或操作符 ---------------------------

/*

question:

create a mask, from start to end, set to 1

start: 1, end: 2 -> 0000,0110

solution: 使用异或

1. get a left

set [0, end] to all 1

2. get a right

set [0, start] to all 1

3. return left ^ right (exclusive operation)

*/

uint32_t setMask_AllOne(uint32_t start, uint32_t end) {

if(start >= 31 || end >= 31) {

return 0;

}

uint32_t left = (1 << start + 1) - 1;

uint32_t right = (1 << end) - 1;

// return left ^ right; // also works

return left - right;

}

/*

question:

create a mask, from start to end, set to 0

start: 1, end: 2 -> 1111,1001

solution:

直接将setMask取反。

*/

uint32_t setMask_AllZero(uint32_t start, uint32_t end) {

return ~setMask_ALLOne(start, end);

}

// ----------------- solution 2: 使用~0这个max来对left和right 来进行操作---------------------------

uint32_t setMask_AllZero(uint32_t start, uint32_t end) {

int max = ~0;

int left = max - ((1 << j) - 1);

int right = ((1 << i) - 1);

int mask = lef | right; //i和j之间，全0

return mask;

}

/*

You are given two 32-bit numbers, N and M, and two bit positions,

i and j Write a method to set all bits between i and j in N equal to M

(e g , M becomes a substring of N located at i and starting at j)

EXAMPLE:Input: N = 10000000000, M = 10101, i = 2, j = 6Output: N = 10001010100

*/

uint32_t updateBits(int n, int m, int i, int j) {

uint32_t mask = setMask_AllZero(i, j);

return (n & mask) | (m << i);

}