[leetcode刷题系列]Merge Sorted Array

class Solution {
public:
void merge(int A[], int m, int B[], int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
// at first, move element of a back
for(int i = m - 1; i >= 0; -- i)
A[i + n] = A[i];
int pa = n, pa_end = m + n;
int pb = 0, pb_end = n;
int valid = 0;
for(; pa < pa_end && pb < pb_end;){
if(A[pa] < B[pb])
A[valid ++ ] = A[pa ++ ];
else
A[valid ++ ] = B[pb ++ ];
}
while(pa < pa_end)
A[valid ++ ] = A[pa ++ ];
while(pb < pb_end)
A[valid ++ ] = B[pb ++ ];
}
};