Как распарсить этот JSON с помощью boost::ptree, c++ так, чтобы можно было вытащить пары после b и пары после a если они есть?
{"stream":"btcusdt@depth@100ms","data":{"e":"depthUpdate","E":1604921041149,"s":"BTCUSDT","U":6511117685,"u":6511117709,"b":[["15516.86000000","3.17375700"],["15516.37000000","2.01556300"],["15515.79000000","0.15500000"],["15515.32000000","0.20000000"],["15515.28000000","0.04203500"],["15513.41000000","0.15680600"],["15512.71000000","0.11427900"],["15512.21000000","0.00000000"],["15511.24000000","0.00200000"]],"a":[["15516.87000000","0.58146800"],["15520.91000000","0.00000000"],["15521.00000000","1.00096800"],["15521.13000000","0.05000000"],["15521.48000000","0.01000000"],["15522.14000000","0.00000000"],["15522.80000000","0.00000000"],["15523.20000000","0.00000000"],["15523.28000000","0.01000000"],["15523.68000000","0.76500000"],["17842.58000000","0.91530000"]]}}
